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Reverse Transcriptase (reverse + transcriptase)
Kinds of Reverse Transcriptase Terms modified by Reverse Transcriptase Selected AbstractsCP-MLR/PLS Directed Structure-Activity Modeling of the HIV-1 RT Inhibitory Activity of 2,3-Diaryl-1,3-thiazolidin-4-onesMOLECULAR INFORMATICS, Issue 4 2004Yenamandra Abstract A detailed structure-activity relationship study of the HIV-1 Reverse Transcriptase (RT) inhibitory activity of two series of compounds, 2-(2,6-dihalo phenyl)-3-(substituted pyridin-2-yl)-thiazolidin-4-ones and 2-(2,6-Dihalophenyl)-3-(substituted phenyl)-thiazolidin-4-ones, belonging to 2,3-diaryl-thiazolidin-4-ones in terms of physicochemical and structural descriptors have been carried out using combinatorial protocol interfaced multiple linear regression (CP-MLR) and partial least squares (PLS) analysis. The models developed in the study indicate a preference for hydrophobic compounds for better inhibitory activity. Also, a positive regression coefficient of I2,3, an indicator descriptor meant for the joint disposition of substituents of 2,3-diaryl moieties of thiazolidinones to address their ability in taking a butterfly like conformation, is in agreement with all earlier observations that compounds having the ability to take butterfly like conformation will be showing better inhibitory activity. The identified models suggest that the meta-positions of 3-aryl moiety has the ability to accommodate hydrophobic/ steric groups. The replacement of C2, of 3-phenyl by nitrogen resulted in 3-pyridyl variants of these analogues. Even though from geometry point of view, the phenyls and pyridyls span almost the same structural space and steric features, presence of nitrogen in pyridyls gave them a blend of polarity, electronic features and a different hydrophobicity profile when compared to corresponding phenyl analogue. Furthermore the PLS models, developed from those descriptors took part in CP-MLR models, indicate that most of the descriptors have almost equal influence in accounting for the variation in the activity of these compounds. This suggests that the factors responsible for the variation in the activity have been uniformly distributed across the varying centers of the molecule. The study suggests that thiazolidinones with 3-(pyridin-2-yl) moiety provide scope for further substituent variation to modulate the HIV-1 RT inhibitory activity. [source] Immunohistochemistry and Reverse Transcriptase,Polymerase Chain Reaction as Methods for Diagnostic Determination of Usher Syndrome Type IIa,THE LARYNGOSCOPE, Issue 7 2004Edward Cohn Abstract Objectives/Hypothesis: Patients having null mutations in the USH2A gene do not produce usherin and therefore are not positive for immunohistochemical staining of the usherin protein. Thus, immunostaining for usherin can serve as a reliable diagnostic tool for Usher syndrome type IIa. Study Design: Prospective. Methods: Immunohistochemical staining for usherin was carried out in basement membrane of minor salivary gland tissue from subjects with confirmed Usher syndrome type IIa and from archival minor salivary gland tissue from patients without Usher syndrome as control samples. Quantitative usherin messenger RNA analysis was performed using minor salivary gland biopsy tissue. Results: Five subjects with Usher syndrome type IIa had no immunostaining in minor salivary gland tissue, whereas control minor salivary gland tissue did stain with usherin antibody. No usherin RNA was detected in biopsy specimens from patients with confirmed Usher syndrome IIa. Conclusion: The feasibility was confirmed of diagnosing Usher syndrome type IIa using purified usherin antibody in subjects having two null USH2A mutations. [source] Influence of the Linkage between Leaving Group and Nucleoside on Substrate Efficiency for Incorporation in DNA Catalyzed by Reverse TranscriptaseCHEMBIOCHEM, Issue 10 2010Anne Giraut Abstract An amino acid deoxyadenosine phosphoramidate and the corresponding phosphodiester congener have been synthesized and tested for primer extension by HIV-1 reverse transcriptase. Replacement of the phosphoramidate linkage of L -histidine,dAMP by a phosphodiester linkage was found to have a beneficial influence on the affinity of this substrate towards HIV-1 reverse transcriptase and on the velocity of the nucleotide incorporation reaction. Modifications of the nature of the PX bond can be useful to fine-tune the substrate properties of nucleoside triphosphate analogues. Our results also demonstrate that polymerization pausing observed during the incorporation of leaving group modified dNTPs is not caused by the nature of the linkage. [source] Tetrazole Thioacetanilides: Potent Non-Nucleoside Inhibitors of WT HIV Reverse Transcriptase and Its K103N Mutant.CHEMINFORM, Issue 33 2006Ester Muraglia Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] 2H-Pyrrolo[3,4-b][1,5]benzothiazepine Derivatives as Potential Inhibitors of HIV-1 Reverse Transcriptase.CHEMINFORM, Issue 40 2005Roberto Di Santo Abstract For Abstract see ChemInform Abstract in Full Text. [source] Synthesis of ,-Fluorophenethyl Halopyridyl Thiourea Compounds as Non-nucleoside Inhibitors of HIV-1 Reverse Transcriptase.CHEMINFORM, Issue 49 2004T. K. Venkatachalam Abstract For Abstract see ChemInform Abstract in Full Text. [source] Contribution of Kir3.1, Kir3.2A and Kir3.2C subunits to native G protein-gated inwardly rectifying potassium currents in cultured hippocampal neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2003Joanne L. Leaney Abstract G protein-gated inwardly rectifying potassium (GIRK) channels are found in neurons, atrial myocytes and neuroendocrine cells. A characteristic feature is their activation by stimulation of Gi/o -coupled receptors. In central neurons, for example, they are activated by adenosine and GABA and, as such, they play an important role in neurotransmitter-mediated regulation of membrane excitability. The channels are tetrameric assemblies of Kir3.x subunits (Kir3.1,3.4 plus splice variants). In this study I have attempted to identify the channel subunits which contribute to the native GIRK current recorded from primary cultured rat hippocampal pyramidal neurons. Reverse transcriptase,polymerase chain reaction revealed the expression of mRNA for Kir3.1, 3.2A, 3.2C and 3.3 subunits and confocal immunofluorescence microscopy was used to investigate their expression patterns. Diffuse staining was observed on both cell somata and dendrites for Kir3.1 and Kir3.2A yet that for Kir3.2C was weaker and punctate. Whole-cell patch clamp recordings were used to record GIRK currents from hippocampal pyramidal neurons which were identified on the basis of inward rectification, dependence of reversal potential on external potassium concentration and sensitivity to tertiapin. The GIRK currents were enhanced by the stimulation of a number of Gi/o -coupled receptors and were inhibited by pertussis toxin. In order to ascertain which Kir3.x subunits were responsible for the native GIRK current I compared the properties with those of the cloned Kir3.1 + 3.2A and Kir3.1 + 3.2C channels heterologously expressed in HEK293 cells. [source] The chromosome translocation t(7;11)(p15;p15) in acute myeloid leukemia results in fusion of the NUP98 gene with a HOXA cluster gene, HOXA13, but not HOXA9GENES, CHROMOSOMES AND CANCER, Issue 4 2002Takeshi Taketani The nucleoporin gene NUP98 has been reported to be fused to 9 partner genes in hematologic malignancies with 11p15 translocations. The NUP98-HOXA9 fusion gene has been identified in acute myeloid leukemia (AML) and chronic myelogenous leukemia with t(7;11)(p15;p15). We report here a novel NUP98 partner gene, HOXA13, in a patient with de novo AML having t(7;11)(p15;p15). The HOXA13 gene is part of the HOXA cluster genes and contains 2 exons, encoding a protein of 338 amino acids with a homeodomain. The NUP98-HOXA13 fusion protein consists of the N-terminal phenylalanine-glycine repeat motif of NUP98 and the C-terminal homeodomain of HOXA13, similar to the NUP98-HOXA9 fusion protein. Reverse transcriptase,polymerase chain reaction (RT-PCR) analysis in various leukemic cell lines showed that the HOXA13 gene was expressed significantly more frequently in acute monocytic leukemic cell lines than in other leukemic cell lines (P = 0.039). HOXA13 and three HOXA cluster genes (A9, A10, A11) located at the 5, end of the HOXA9 gene were frequently expressed in myeloid leukemic cell lines. Our results revealed that t(7;11)(p15;p15) was not a single chromosomal abnormality at the molecular level. The protein encoded by the NUP98-HOXA13 fusion gene is similar to that encoded by NUP98-HOXA9, and the expression pattern of the HOXA13 gene in leukemic cell lines is similar to that of the HOXA9 gene, suggesting that the NUP98-HOXA13 fusion protein may play a role in leukemogenesis through a mechanism similar to that of the NUP98-HOXA9 fusion protein. © 2002 Wiley-Liss, Inc. [source] Expression of NUP98/TOP1, but not of TOP1/NUP98, in a treatment-related myelodysplastic syndrome with t(10;20;11)(q24;q11;p15)GENES, CHROMOSOMES AND CANCER, Issue 2 2002Ioannis Panagopoulos The t(11;20)(p15;q11) is a rare but recurrent translocation that so far has been described in only four acute myeloid leukemias (AMLs), two treatment-related myelodysplastic syndromes (t-MDSs), and one case of polycythemia vera. Recently, the t(11;20) was shown to result in a fusion of the NUP98 and TOP1 genes, with expression of the NUP98/TOP1 chimera encoded by the der(11)t(11;20), but not of the reciprocal TOP1/NUP98 on the der(20)t(11;20). The genomic breakpoints were subsequently mapped to introns 13 and 7 of NUP98 and TOP1, respectively. We present here a t-MDS with a three-way variant translocation, t(10;20;11)(q24;q11;p15), that generates a der(11)t(11;20) but not a der(20)t(11;20), strongly suggesting that the der(11) harbors the critical genetic rearrangement. Reverse transcriptase,polymerase chain reaction (RT-PCR) revealed a NUP98/TOP1 fusion in which exon 13 of NUP98 was fused in-frame with exon 8 of TOP1. Extra long (XL) genomic PCR and subsequent sequence analyses showed that the breakpoint in NUP98 occurred at nucleotide (nt) 3461 of intron 13, close to a MER (medium reiteration frequency interspersed repetitive element) repeat, and that the breakpoint in TOP1 was at nt 1436 of intron 7, downstream of a MIR (mammalian-wide interspersed repeats) repetitive element. Genomic XL PCR did not amplify the reciprocal TOP1/NUP98, nor was this chimera expressed, as expected from the cytogenetic finding. The present results provide further support for the involvement of the NUP98/TOP1 transcript, but not of the reciprocal one, in the development of MDS/AML. Furthermore, the three cases genomically characterized to date have all been treatment-related and have all harbored breakpoints in intron 13 of NUP98 and intron 7 of TOP1, suggesting that these introns are susceptible to chemotherapy-induced breakage. © 2002 Wiley-Liss, Inc. [source] Host's innate immune response to fungal and bacterial agents in vitro: up-regulation of interleukin-15 gene expression resulting in enhanced natural killer cell activityIMMUNOLOGY, Issue 2 2003Phay Tran Summary Natural killer (NK) cells play an important role in the first line of defence against viral infections. We have shown earlier that exposure of human peripheral blood mononuclear cells (PBMC) to viruses results in rapid up-regulation of NK cell activity via interleukin-15 (IL-15) induction, and that this mechanism curtails viral infection in vitro. By using Candida albicans, Escherichia coli and Staphylococcus aureus, we now show here that exposure of PBMC to fungi and bacteria also results in an immediate increase of NK cytotoxicity. Reverse transcriptase,polymerase chain reaction and Western blot analyses as well as the use of antibodies against different cytokines revealed that IL-15 induction played a predominant role in this NK activation. These results indicate that IL-15 is also involved in the innate immune response against fungal and bacterial agents. [source] Expression of aquaporin 8 is diversely regulated by osmotic stress in amnion epithelial cellsJOURNAL OF OBSTETRICS AND GYNAECOLOGY RESEARCH (ELECTRONIC), Issue 6 2009Hongbo Qi Abstract Aim:, Water absorption across fetal chorioamniotic membranes is a critical regulatory pathway for amniotic fluid volume homeostasis. Aquaporin 8 (AQP8) is a water channel regulating osmotic water travel across membranes. This study was to investigate the distribution and expression of AQP8 in amnion epithelial cells (AEC) in response to different osmotic stresses. Methods:, Cells derived from the amnion were subjected to different osmotic culture media. Reverse transcriptase,polymerase chain reaction, Western blotting and immunofluorescence analysis were used to determine expression and localization of AQP8. Results:, Immunofluorescent staining confirmed the expression of AQP8 on cytomembrane and in cytoplasm. Hypotonic media increased AQP8 on cytomembrane of AEC. Compared to isosmolar media, hypotonic media significantly enhanced AQP8 mRNA and protein expression (P < 0.05), while hypertonic media significantly decreased expression (P < 0.05). Conclusion:, The expression and distribution of AQP8 in AEC are diversely regulated by osmotic loads suggesting a role for AQP8 in intramembranous water transport and the balance of amniotic fluid. [source] Establishment and characterization of a KIT-positive and stem cell factor-producing cell line, KTHOS, derived from human osteosarcomaPATHOLOGY INTERNATIONAL, Issue 2 2005Toshiaki Hitora Osteosarcoma is a malignant bone tumor that commonly affects adolescents and young adults. In the present study a human osteosarcoma cell line, KTHOS, was established from a primary osteosarcoma lesion in the distal femur of a 16-year-old girl. After 106 passages, the KTHOS cell line retained the biological characteristics of osteosarcoma. The KTHOS cells had spindle to pleomorphic cytoplasm with round to ovoid nuclei containing multiple prominent nucleoli, as expected based on the mesodermic origin of osteoblasts. The KTHOS cells were immunoreactive for osteocalcin, osteonectin, stem cell factor (SCF), and KIT (CD117). Reverse transcriptase,polymerase chain reaction indicated that the KTHOS cell line expressed mRNA for SCF and KIT. The KTHOS cells produced relatively high amounts of soluble SCF as determined by enzyme-linked immunosorbent assay. The results suggest that cell proliferation of the KTHOS cell line might be involved in autocrine and/or paracrine loops of the SCF/KIT signaling system. The KTHOS cell line is a novel human osteosarcoma cell line that releases SCF and expresses KIT. This cell line can be used for studies to explore the mechanisms for oncogenesis of human osteosarcomas. [source] Mesenteric transection decreases expression of interstitial cells of Cajal in an experimental modelBRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 4 2007M. Nishimura Background: After anterior resection for rectal carcinoma patients often complain of defaecatory dysfunction. The aim of this study was to examine the number of interstitial cells of Cajal (ICCs) and ganglion cells in the distal colon partially denervated by mesenteric transection in a rat model. Methods: Four groups of rats were operated on, a control group and three experimental groups, with increasing degree of mesenteric transection to denervate the distal colon. Animals were killed after 3 months, and the denervated colon was investigated using immunohistochemistry with Kit and protein gene product 9.5 antibodies to detect ICCs and ganglion cells respectively. Reverse transcriptase,polymerase chain reaction for c-kit and histomorphometry of muscular thickness were performed. Results: The total number of ICCs was significantly lower in the three operated models than in the control, particularly in the histological layers of the myenteric plexus and submucosal border. There was no difference in the number of ganglion cells or changes in muscular thickness between the models. Conclusion: The number of ICCs in rat distal colon denervated by mesenteric transection is decreased at 3 months after surgery. Copyright © 2007 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd. [source] Over-expression of cysteine proteinase inhibitor cystatin 6 promotes pancreatic cancer growthCANCER SCIENCE, Issue 8 2008Masayo Hosokawa Pancreatic ductal adenocarcinoma (PDAC) shows the worst mortality among the common malignancies and development of novel therapies for PDAC through identification of good molecular targets is an urgent issue. Among dozens of over-expressing genes identified through our gene-expression profile analysis of PDAC cells, we here report CST6 (Cystatin 6 or E/M) as a candidate of molecular targets for PDAC treatment. Reverse transcriptase,polymerase chain reaction (RT-PCR) and immunohistochemical analysis confirmed over-expression of CST6 in PDAC cells, but no or limited expression of CST6 was observed in normal pancreas and other vital organs. Knock-down of endogenous CST6 expression by small interfering RNA attenuated PDAC cell growth, suggesting its essential role in maintaining viability of PDAC cells. Concordantly, constitutive expression of CST6 in CST6-null cells promoted their growth in vitro and in vivo. Furthermore, the addition of mature recombinant CST6 in culture medium also promoted cell proliferation in a dose-dependent manner, whereas recombinant CST6 lacking its proteinase-inhibitor domain and its non-glycosylated form did not. Over-expression of CST6 inhibited the intracellular activity of cathepsin B, which is one of the putative substrates of CST6 proteinase inhibitor and can intracellularly function as a pro-apoptotic factor. These findings imply that CST6 is likely to involve in the proliferation and survival of pancreatic cancer probably through its proteinase inhibitory activity, and it is a promising molecular target for development of new therapeutic strategies for PDAC. (Cancer Sci 2008; 99: 1626,1632) [source] Prevalence of hepatitis B virus DNA polymerase mutations in treatment-naïve patients with chronic hepatitis BALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 11-12 2009M. H. NGUYEN Summary Background, One of the most important factors in treatment failure using nucleos(t)ide analogues in chronic hepatitis B is anti-viral resistance. Primary drug resistance refers to amino acid changes in the hepatitis B virus polymerase/reverse transcriptase (rt) that result in reduced susceptibility to anti-viral agents. Pre-existing drug resistance mutations may occur in untreated patients and may affect their treatment outcomes. Aim, To determine the prevalence of hepatitis B DNA polymerase mutations in treatment-naïve patients. Methods, We used a direct PCR sequencing test to detect DNA polymerase mutations in 472 consecutive treatment-naïve patients at two community gastroenterology clinics in Northern California. Results, A majority of patients were Asians (>95%), had either genotype B or C (95%) and had no evidence of cirrhosis or liver cancer (94%). Mean age was 45 ± 13 and mean hepatitis B virus DNA was 5.3 ± 1.8 log10 IU/mL. Most patients did not have any detectable mutations (82.4%). Some (16.7%) had mutations of unknown clinical significance (rtV207M/L/I) and only 4 patients had rtA181A/S, rtA194S or M250I. Conclusions, No rtM204V/I or rtN236T mutations were observed in our study. Less than 1% of our patients had mutations that can be associated with primary resistance to existing anti-viral therapies for hepatitis B virus. [source] Clinical significance of bone marrow micrometastases in esophageal cancerDISEASES OF THE ESOPHAGUS, Issue 4 2004H. Inoue SUMMARY, Using the reverse transcriptase,polymerase chain reaction (RT-PCR), we investigated the clinical significance of bone marrow micrometastases in patients with esophageal cancer. Bone marrow samples from 57 patients with esophageal cancer, who underwent esophagotomy, were investigated by specific RT-PCR for carcinoembryonic antigens (CEA). A total of 40 out of 57 patients (70.1%) were positive for CEA mRNA in the bone marrow. Among curatively resected cases, 34 of 50 patients (68.0%) were positive for CEA. Ten of 13 T1 patients (76.9%) were positive for CEA. Although the CEA-positive rate was high, there was no significant correlation between CEA positivity and any clinical characteristics. Among the 40 CEA-positive patients, 50% have shown recurrence so far. Detection of cancer cells in the bone marrow by RT-PCR may not always correspond to the malignant potential or other characteristics of the tumor. CEA-positive ,micrometastases' might actually represent isolated circulating tumor cells without much biological significance. [source] Study of binding stoichiometries of the human immunodeficiency virus type,1 reverse transcriptase by capillary electrophoresis and laser-induced fluorescence polarization using aptamers as probesELECTROPHORESIS, Issue 2 2006Hao Fu Abstract Binding stoichiometries between four DNA aptamers (RT12, RT26, RTlt49, and ODN93) and the reverse transcriptase (RT) of the type,1 human immunodeficiency virus (HIV-1) were studied using affinity CE (ACE) coupled with LIF polarization and fluorescence polarization (FP). The ACE/LIF study showed evidence of two binding stoichiometries between the HIV-1,RT protein and aptamers RT12, RT26, and ODN93, suggesting that these aptamers can bind to both the p66 and p51 subunits of the HIV-1,RT. Only one binding stoichiometry for aptamer RTlt49 was found. The affinity complexes were easily separated from the unbound aptamers; however, the different stoichiometries were not well resolved. A complementary technique, FP, was able to provide additional information about the binding and supporting evidence for the ACE/LIF results. The ACE/LIFP study also revealed that the FP values of the 1:1 complexes of the HIV-1,RT protein with aptamers RT12, RT26, and ODN93 were always much greater than those of the 1:2 complexes. This was initially surprising because the larger molecular size of the 1:2 complexes was expected to result in higher FP values than the corresponding 1:1 complexes. This phenomenon was probably a result of fluorescence resonance energy transfer between the two fluorescent molecules bound to the HIV-1,RT protein. [source] Double Cyclization of Bis(,-hetarylmethyl)amino Esters to Optically Active Bridged N-Heterocycles of HIV-Inhibiting ActivityEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 16 2004Heike Faltz Abstract Anellated 1-azabicyclo[3.3.1]nonanes 6 were synthesized by several routes starting from natural ,-amino esters 2 and o -haloaryl- or o -bromohetarylmethyl bromides 1. N -Alkylation of the starting amino esters to 5 and 3 was followed by halogen/lithium exchange and double cyclization. The cyclization products 6 exhibit interesting inhibition of RNase H and DNA-polymerase activity of reverse transcriptase (RT) of HIV-1 at concentrations where human cellular DNA polymerases are not affected. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Tissue-specific regulation of ACE/ACE2 and AT1/AT2 receptor gene expression by oestrogen in apolipoprotein E/oestrogen receptor-, knock-out miceEXPERIMENTAL PHYSIOLOGY, Issue 5 2008K. Bridget Brosnihan Angiotensin-converting enzyme (ACE) and ACE2 and the AT1 and AT2 receptors are pivotal points of regulation in the renin,angiotensin system. ACE and ACE2 are key enzymes in the formation and degradation of angiotensin II (Ang II) and angiotensin-(1,7)(Ang-(1,7)). Ang II acts at either the AT1 or the AT2 receptor to mediate opposing actions of vasoconstriction or vasodilatation respectively. While it is known that oestrogen acts to downregulate ACE and the AT1 receptor, its regulation of ACE2 and the AT2 receptor and the involvement of a specific oestrogen receptor subtype are unknown. To investigate the role of oestrogen receptor-, (ER,) in the regulation by oestrogen of ACE/ACE2 and AT1/AT2 mRNAs in lung and kidney, ovariectomized female mice lacking apolipoprotein E (ee) with the ER, (AAee) or without the ER, (,,ee) were treated with 17,-oestradiol (6 ,g day,1) or placebo for 3 months. ACE, ACE2, AT1 receptor and AT2 receptor mRNAs were measured using reverse transcriptase, real-time polymerase chain reaction. In the kidney, 17,-oestradiol showed 1.7-fold downregulation of ACE mRNA in AAee mice, with 2.1-fold upregulation of ACE mRNA in ,,ee mice. 17,-Oestradiol showed 1.5- and 1.8-fold downregulation of ACE2 and AT1 receptor mRNA in AAee mice; this regulation was lost in ,,ee mice. 17,-Oestradiol showed marked (81-fold) upregulation of the AT2 receptor mRNA in AAee mice. In the lung, 17,-oestradiol treatment had no effect on AT1 receptor mRNA in AAee mice, but resulted in a 1.5-fold decreased regulation of AT1 mRNA in ,,ee mice. There was no significant interaction of oestrogen with ER, in the lung for ACE, ACE2 and AT2 receptor genes. These studies reveal tissue-specific regulation by 17,-oestradiol of ACE/ACE2 and AT1/AT2 receptor genes, with the ER, receptor being primarily responsible for the regulation of kidney ACE2, AT1 receptor and AT2 receptor genes. [source] A role for endogenous reverse transcriptase in tumorigenesis and as a target in differentiating cancer therapyGENES, CHROMOSOMES AND CANCER, Issue 1 2006Paola Sinibaldi-Vallebona An unexpected result emerging from completion of the genome sequencing project is that a large portion of mammalian genomes is constituted by retrotransposons. A large body of published data supports the conclusion that retrotransposons are biologically active elements and indicates that retrotransposition is an ongoing process in mammalian genomes. Retroelements can act as insertional mutagens altering the coding integrity of genes and, recently, have been found to also affect the expression of cellular genes at the epigenetic level: in this light, they are a potential threat in that these events can trigger the onset of several pathologies including cancer. Retroelement genes, and particularly the gene coding for reverse transcriptase (RT), are typically expressed at high levels in transformed cells and tumors. In recent work, we have found that drug-mediated inhibition of the endogenous RT activity, or silencing of expression of active retrotransposons of the LINE-1 family by RNA interference, down-regulate cell growth and induce the activation of differentiating functions in several cancer cell lines. Moreover, the inhibition of endogenous RT activity in vivo antagonizes the growth of human tumors in animal models. In this review, we discuss newly emerging concepts on the role of retrotransposons and suggest that an abnormally high level of the RT activity that they encode may contribute to the loss of control in the proliferation and differentiation programs typical of transformed cells. In this light, RT-coding elements may be regarded as promising targets in the development of novel, differentiation-inducing approaches to cancer therapy. © 2005 Wiley-Liss, Inc. [source] MLL/SEPTIN6 chimeric transcript from inv ins(X;11)(q24;q23q13) in acute monocytic leukemia: Report of a case and review of the literatureGENES, CHROMOSOMES AND CANCER, Issue 1 2003Hee-Jin Kim Rearrangements of the MLL gene on chromosome 11, band q23, are one of the most common genetic changes in acute leukemia. Reciprocal translocation is the most common form of MLL rearrangement, and the partner genes in MLL translocation are notably diverse. Involvement of the SEPTIN6 gene on Xq24 in MLL rearrangements occurs very rarely, with only six cases having been documented in the literature. Of note, the MLL/SEPTIN6 rearrangements in these cases were cryptic or complex, and it was shown that the 5,- MLL/SEPTIN6 -3, transcript resides on the derivative X chromosome rather than on the derivative chromosome 11 as in the majority of cases of MLL translocations. These observations suggested that MLL and SEPTIN6 reside on their respective chromosome loci in reverse orientation, that is, centromere-to-telomere and telomere-to-centromere, respectively. We here report a case of acute monocytic leukemia with inv ins(X;11)(q24;q23q13) in a 29-month-old child. Fluorescence in situ hybridization study revealed the break-apart 5,- MLL segment to be translocated to the derivative X chromosome, and reverse transcriptase,polymerase chain reaction followed by sequencing analysis confirmed the 5,- MLL/SEPTIN6 -3, chimeric transcript. This case is the first to provide direct cytogenetic evidence for the salient nature of the MLL/SEPTIN6 rearrangement. We reviewed clinical and cytogenetic features of all cases of 11q23 and Xq22,24 rearrangements reported up to now, including six cases where the involvement of the SEPTIN6 gene was confirmed by molecular techniques. © 2003 Wiley-Liss, Inc. [source] Amplification of the telomerase reverse transcriptase (hTERT) gene in cervical carcinomasGENES, CHROMOSOMES AND CANCER, Issue 3 2002Anju Zhang The expression of telomerase reverse transcriptase (hTERT), the catalytic component of the telomerase complex, is required for activation of telomerase during immortalization and transformation of human cells. However, the biochemical and genetic mechanisms governing hTERT expression remain to be elucidated. In the present study, we examined hTERT amplification as a potential genetic event contributing to telomerase activation in cervical carcinomas. An amplification of the hTERT gene was found in 1/4 cervical cancer cell lines and 21/88 primary tumor samples derived from the patients with cervical carcinomas. An increase in the hTERT copy number was significantly correlated with higher levels of hTERT protein expression. Moreover, the hTERT alterations with the enhanced hTERT expression were exclusively observed in those tumors with high-risk human papillomavirus infection. Taken together, the hTERT gene amplification, directly or indirectly targeted by human papillomavirus, may be one of the driving forces responsible for upregulation of hTERT expression and activation of telomerase in cervical cancers. © 2002 Wiley-Liss, Inc. [source] Spontaneous HBeAg seroconversion and loss of hepatitis B virus DNA after acute flare due to development of drug resistant mutants during entecavir monotherapyHEPATOLOGY RESEARCH, Issue 1 2009Ri-Cheng Mao Aims:, Patients with chronic hepatitis B virus (HBV) infection under entecavir (ETV) treatment develop resistant mutants with viral rebound. Here, we report an interesting case of spontaneous loss of HBV-DNA and seroconversion following an acute flare after the development of ETV-resistant mutants. This patient received ETV after lamivudine breakthrough. Methods:, Cloning and sequence analysis of the HBV reverse transcriptase (RT) region were performed with seven samples during ETV therapy. In addition, two full-length HBV genomes derived from samples before and after the emergence of ETV resistance were sequenced. Results:, ETV resistant mutants appeared at week 228, with virological and biochemical rebound at the same time. Unexpectedly, HBeAg seroconversion occurred 8 weeks later. The viral load decreased and became undetectable from week 252. Analysis of HBV isolates in the patient at week 124 revealed that wild-type HBV was predominant at that time and ETV resistant mutants were not found among 20 clones. Interestingly, a new mutant type with rtL180M+rtT184L was found alongside rtL180M+rtT184L+rtM204V/I at week 228 and appeared to develop independently, according to the sequence analysis. In contrast to the previously identified ETV resistant mutants, it did not carry the rtM204V/I mutations. Conclusion:, The data presented here indicates that the flare following the emergence of ETV resistant mutants may reflect immune-mediated control of HBV infection, leading to a spontaneous loss of HBV-DNA and seroconversion. [source] Effect of concurrent zidovudine use on the resistance pathway selected by abacavir-containing regimensHIV MEDICINE, Issue 6 2004ER Lanier Objectives Abacavir (ABC) selects for four mutations (K65R, L74V, Y115F and M184V) in HIV-1 reverse transcriptase (RT), both in vitro and during monotherapy in vivo. The aim of this analysis was to compare the selection of these and other nucleoside reverse transcriptase inhibitor (NRTI)-associated mutations by ABC-containing therapies in the presence and absence of concurrent lamivudine (3TC) and/or zidovudine (ZDV) and to assess the effect of these mutations on phenotypic susceptibility to the NRTIs. Design This study was a retrospective analysis of the patterns of NRTI-associated mutations selected following virological failure in six multicentre trials conducted during the development of ABC. Methods Virological failure was defined as confirmed vRNA above 400 HIV-1 RNA copies/mL. RT genotype and phenotype were determined using standard methods. Results K65R was selected infrequently by ABC-containing regimens in the absence of ZDV (13 of 127 patients), while L74V/I was selected more frequently (51 of 127 patients). Selection of both K65R and L74V/I was significantly reduced by co-administration of ZDV with ABC (one of 86 and two of 86 patients, respectively). Y115F was uncommon in the absence (seven of 127 patients) or presence (four of 86 patients) of ZDV. M184V was the most frequently selected mutation by ABC alone (24 of 70 patients) and by ABC plus 3TC (48 of 70 patients). Thymidine analogue mutations were associated with ZDV use. The K65R mutation conferred the broadest phenotypic cross-resistance of the mutations studied. Conclusions The resistance pathway selected upon virological failure of ABC-containing regimens is significantly altered by concurrent ZDV use, but not by concurrent 3TC use. These data may have important implications for the efficacy of subsequent lines of NRTI therapies. [source] The prevalence of reduced zidovudine susceptibility in zidovudine-naive, antiretroviral-experienced HIV-1-infected patientsHIV MEDICINE, Issue 4 2003Y Gilleece Objectives There is increasing in vitro and in vivo evidence that reduced zidovudine (ZDV) susceptibility is generated by the selective pressure conferred by other nucleoside reverse transcriptase inhibitors (NRTIs). However, the degree to which this occurs in clinical practice remains unclear. We assessed phenotypic and genotypic resistance in ZDV-naive patients with virological failure on stavudine (d4T)-containing regimens, with particular reference to potential cross-resistance between d4T and ZDV. Methods Patients were identified from a clinical database. Treatment history was confirmed by case note evaluation and discussion with patients. Genotypic and phenotypic analyses were undertaken by Virco (Virco BVBA, Mechelen, Belgium). Results Sixty-seven drug-experienced, ZDV-naive patients who underwent a resistance test while failing a d4T-containing regimen were identified. Of these patients, 23% had received three or more NRTIs and 42% at least one non-nucleoside reverse transcriptase (RT) inhibitor; 22% had viruses with reduced d4T susceptibility (>1.8-fold resistance), and 25% had viruses with reduced ZDV susceptibility (>4-fold). The most frequently observed RT mutations were identified. A significant correlation was found between susceptibility to d4T and susceptibility to ZDV (r=0.36; P=0.003), and also between virtual resistance to d4T and that to ZDV (r=0.38; P=0.002). Conclusions A significant minority of d4T-treated, ZDV-naive patients were found to have viruses with reduced ZDV susceptibility, with a variable association with classical ZDV resistance mutations. These data suggest that cross-resistance between d4T and ZDV may involve novel constellations of mutations. Correlations between d4T and ZDV susceptibilities and resistances further support cross-resistance between NRTIs. [source] HIV-related morbidity and mortality in patients starting protease inhibitors in very advanced HIV disease (CD4 count of <,50 cells/µL): an analysis of 338 clinical events from a randomized clinical trial,HIV MEDICINE, Issue 2 2002M Floridia Background AIDS defining events occur infrequently in the presence of CD4 counts above 200 cells/µL. It is, however, uncertain for most of the AIDS defining conditions whether this threshold can be considered equally safe in patients with a previously very low CD4 nadir. Methods We evaluated in detail all the AIDS defining events observed during a 48-week clinical trial in 1251 nucleoside reverse transcriptase inhibitor-experienced patients who started protease inhibitors (PIs) at CD4 counts below 50 cells/µL. The type of event, immunological status at the moment of event and time between start of PI treatment and event occurrence were analysed cumulatively and by event type; event rates were calculated. Results Concomitant data on CD4 counts were available for 338 AIDS defining events (81% of total events). Median time between start of treatment with PI and event was 94.5 days and median absolute CD4 value at the occurrence of event was 20 per µL. Only 14 events (in 12 patients) were observed above the threshold of 200 CD4 cells/µL. An analysis of the 67 deaths with concomitantly available CD4 counts (57%) showed a median CD4 count of 10 cells/µL, with only four deaths occurring in the presence of a CD4 count above 100 cells/µL. Conclusions Very few clinical AIDS defining conditions were observed in patients who start PIs at very low CD4 counts and with treatment restore absolute values in CD4 counts above 200 cells/µL. This threshold can therefore be considered a clinically effective goal of treatment with respect to occurrence of all AIDS defining conditions in patients starting PIs in very advanced HIV disease. [source] Ex vivo expanded cord blood CD4 T lymphocytes exhibit a distinct expression profile of cytokine-related genes from those of peripheral blood originIMMUNOLOGY, Issue 3 2009Yoshitaka Miyagawa Summary With an increase in the importance of umbilical cord blood (CB) as an alternative source of haematopoietic progenitors for allogenic transplantation, donor lymphocyte infusion (DLI) with donor CB-derived activated CD4+ T cells in the unrelated CB transplantation setting is expected to be of increased usefulness as a direct approach for improving post-transplant immune function. To clarify the characteristics of activated CD4+ T cells derived from CB, we investigated their mRNA expression profiles and compared them with those of peripheral blood (PB)-derived activated CD4+ T cells. Based on the results of a DNA microarray analysis and quantitative real-time reverse transcriptase,polymerase chain reaction (RT-PCR), a relatively high level of forkhead box protein 3 (Foxp3) gene expression and a relatively low level of interleukin (IL)-17 gene expression were revealed to be significant features of the gene expression profile of CB-derived activated CD4+ T cells. Flow cytometric analysis further revealed protein expression of Foxp3 in a portion of CB-derived activated CD4+ T cells. The low level of retinoic acid receptor-related orphan receptor , isoform t (ROR,t) gene expression in CB-derived activated CD4+ T cells was speculated to be responsible for the low level of IL-17 gene expression. Our data indicate a difference in gene expression between CD4+ T cells from CB and those from PB. The findings of Foxp3 expression, a characteristic of regulatory T cells, and a low level of IL-17 gene expression suggest that CB-derived CD4+ T cells may be a more appropriate source for DLI. [source] Characterization of cells of the B lineage in the human adult greater omentumIMMUNOLOGY, Issue 1 2006Laurent Boursier Summary Peritoneal B cells and their omental precursors play an important role in the immune response of the peritoneal cavity and mucosal surfaces in mice. We have previously shown that peritoneal and mucosal B lineage cells are unlikely to be significantly linked in humans. However, the status of the omentum remains unknown. Here, using immunohistochemistry, we observed that sparse, quiescent B cells and occasional clusters of B cells were present in the omentum and that plasma cells, predominantly with cytoplasmic immunoglobulin G (IgG), were present. We analysed sequences of immunoglobulin genes amplified using reverse transcriptase,polymerase chain reaction (RT-PCR) from the normal human greater omentum, and describe the characteristics of variable region genes used by IgG, IgA and IgM. We focused on the properties of IgVH4 and IgVH5 families to allow comparisons of like with like between different Ig isotypes and cells from different immune compartments. We observed that the IgM genes were derived from a mixed population with mutated and unmutated immunoglobulin sequences. All IgVH4 and IgVH5 genes used by IgA and IgG from omental cells showed evidence of somatic hypermutation but the load of mutations was not significantly different to that seen in either the systemic or the mucosal compartments. The trends observed, including the dominance of IgG plasma cells, the IgA1/IgA2 ratio being biased towards IgA1, JH1 usage, and a moderate level of somatic mutations, link omental B lineage cells with the systemic compartment. These observations reinforce previous studies highlighting the difference between human and murine B-cell compartments and their relationship to the mucosal immune system. [source] Immune-privileged embryonic Swiss mouse STO and STO cell-derived progenitor cells: major histocompatibility complex and cell differentiation antigen expression patterns resemble those of human embryonic stem cell linesIMMUNOLOGY, Issue 1 2006Katherine S. Koch Summary Embryonic mouse STO (S, SIM; T, 6-thioguanine resistant; O, ouabain resistant) and 3(8)21-enhanced green fluorescent protein (EGFP) cell lines exhibit long-term survival and hepatic progenitor cell behaviour after xenogeneic engraftment in non-immunosuppressed inbred rats, and were previously designated major histocompatibility complex (MHC) class I- and class II-negative lines. To determine the molecular basis for undetectable MHC determinants, the expression and haplotype of H-2K, H-2D, H-2L and I-A proteins were reassessed by reverse transcriptase,polymerase chain reaction (RT-PCR), cDNA sequencing, RNA hybridization, immunoblotting, quantitative RT-PCR (QPCR), immunocytochemistry and flow cytometry. To detect cell differentiation (CD) surface antigens characteristic of stem cells, apoptotic regulation or adaptive immunity that might facilitate progenitor cell status or immune privilege, flow cytometry was also used to screen untreated and cytokine [interferon (IFN)-,]-treated cultures. Despite prior PCR genotyping analyses suggestive of H-2q haplotypes in STO, 3(8)21-EGFP and parental 3(8)21 cells, all three lines expressed H-2K cDNA sequences identical to those of d-haplotype BALB/c mice, as well as constitutive and cytokine-inducible H-2Kd determinants. In contrast, apart from H-2Ld[LOW] display in 3(8)21 cells, H-2Dd, H-2Ld and I-Ad determinants were undetectable. All three lines expressed constitutive and cytokine-inducible CD34; however, except for inducible CD117[LOW] expression in 3(8)21 cells, no expression of CD45, CD117, CD62L, CD80, CD86, CD90·1 or CD95L/CD178 was observed. Constitutive and cytokine-inducible CD95[LOW] expression was detected in STO and 3(8)21 cells, but not in 3(8)21-EGFP cells. MHC (class I+[LOW]/class II,) and CD (CD34+/CD80,/CD86,/CD95L,) expression patterns in STO and STO cell-derived progenitor cells resemble patterns reported for human embryonic stem cell lines. Whether these patterns reflect associations with mechanisms that are regulatory of immune privilege or functional tissue-specific plasticity is unknown. [source] Expression and regulation of the pattern recognition receptors Toll-like receptor-2 and Toll-like receptor-4 in the human placentaIMMUNOLOGY, Issue 1 2002Ulrika Holmlund Summary The placenta constitutes a physical and immunological barrier against invading infectious agents and has been suggested to be a pregnancy-specific component of the innate immune system. The aim of this study was to investigate the presence and regulation of Toll-like receptors-2 and -4 (TLR2 and TLR4) in the human placenta, because these receptors are believed to be important for immune responses against pathogens. Twenty-eight placentas from normal term pregnancies were analysed with immunohistochemistry, which showed a strong immunoreactivity for TLR2 and TLR4 in the villous and the intermediate trophoblasts. The regulation of TLR2 and TLR4 by microbial stimulus was assessed by incubating explants of term chorionic villi with zymosan or lipopolysaccharide (LPS) and analysed with real-time reverse transcriptase,polymerase chain reaction. Stimulation with zymosan and LPS readily induced interleukin (IL)-6 and IL-8 cytokine production in the placenta cultures, whereas TLR2 and TLR4 mRNA and protein expression remained at the same high level as in unstimulated explants. These data suggests a novel mechanism for the fetoplacental unit to interact with micro-organisms. [source] | |||||||||||||||||||||||||||||||||||||