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Cell-cycle Control (cell-cycle + control)
Selected AbstractsCaffeine mimics adenine and 2,-deoxyadenosine, both of which inhibit the guanine-nucleotide exchange activity of RCC1 and the kinase activity of ATRGENES TO CELLS, Issue 5 2003Hitoshi Nishijima Background: Both caffeine and the inactivation of RCC1, the guanine-nucleotide exchange factor (GEF) of Ran, induce premature chromatin condensation (PCC) in hamster BHK21 cells arrested in the S-phase, suggesting that RCC1 is a target for caffeine. Results: Caffeine inhibited the Ran-GEF activity of RCC1 by preventing the binary complex formation of Ran-RCC1. Inhibition of the Ran-GEF activity of RCC1 by caffeine and its derivatives was correlated with their ability to induce PCC. Since caffeine is a derivative of xanthine, the bases and nucleosides were screened for their ability to inhibit RCC1. Adenine, adenosine, and all of the 2,-deoxynucleosides inhibited the Ran-GEF activity of RCC1; however, only adenine and 2,-deoxyadenosine (2,-dA) induced PCC. A factor(s) other than RCC1, should therefore be involved in PCC-induction. We found that both adenine and 2,-dA, but none of the other 2,-deoxynucleosides, inhibited the kinase activity of ATR, similar to that of caffeine. The ATR pathway was also abrogated by the inactivation of RCC1 in tsBN2 cells. Conclusion: The effect of caffeine on cell-cycle control mimics the biological effect of adenine and 2,-dA, both of which inhibit ATR. dATP, a final metabolite of adenine and 2,-dA, is suggested to inhibit ATR, resulting in PCC. [source] p73 G4C14-to-A4T14 polymorphism and risk of second primary malignancy after index squamous cell carcinoma of head and neckINTERNATIONAL JOURNAL OF CANCER, Issue 11 2009Fanglin Li Abstract P73 plays an important role in modulating cell-cycle control, inducing apoptosis, and inhibiting cell growth. A novel noncoding p73 G4C14-to-A4T14 exon 2 polymorphism was associated with risk of squamous cell carcinoma of the head and neck (SCCHN). We hypothesized that p73 G4C14-to-A4T14 polymorphism modulates risk of second primary malignancies (SPM) in patients after index SCCHN. We followed a cohort of 1,384 patients diagnosed with incident SCCHN between May 1995 and January 2007 for SPM development. Log-rank test and Cox proportional hazard models were used to compare SPM-free survival and SPM risk between the different genotype groups. Our results showed that patients carrying the p73 variant AT allele were less likely to develop SPM compared with the patients with p73 GC/GC genotype (Log-rank test, p = 0.013). Compared with the p73 GC/GC genotype, there was a significantly reduced risk of SPM associated with the p73 GC/AT genotype (HR, 0.61, 95% CI, 0.40,0.93) and the combined p73 GC/AT+AT/AT genotypes (HR, 0.59, 95% CI, 0.39,0.89), but a nonsignificantly reduced risk for p73 AT/AT genotype (HR, 0.44, 95% CI, 0.14,1.41). The p73 AT allele was significantly associated with risk of SPM in an allele dose-response manner (p = 0.011 for trend). The risk of SPM associated with p73 variant genotypes (GC/AT+AT/AT) was more pronounced in several subgroups (e.g., older patients, men, minorities, ever smokers, and ever drinkers). Our results support that this p73 polymorphism may be a marker for risk of SPM among patients with an incident SCCHN. © 2009 UICC [source] BRCA1-IRIS activates cyclin D1 expression in breast cancer cells by downregulating the JNK phosphatase DUSP3/VHRINTERNATIONAL JOURNAL OF CANCER, Issue 1 2007Lu Hao Abstract Cyclin D1 plays an important role in cell cycle progression. In breast cancer, Cyclin D1 expression is deregulated by several mechanisms. We previously showed that in breast cancer cells, overexpression of BRCA1-IRIS induces Cyclin D1 overexpression and increases cell proliferation. BRCA1-IRIS alone or in complex with steroid receptor co-activators was targeted to the cyclin D1 promoter pre-bound by the c-Jun/AP1 and activated its transcription, which could explain the co-overexpression of BRCA1-IRIS and Cyclin D1 in breast cancer cells coupled with their increased proliferation. We report here an alternate or a complementary pathway by which BRCA1-IRIS activates Cyclin D1 expression. BRCA1-IRIS overexpression decreases the expression of the dual specificity phosphatase, DUSP3/VHR, an endogenous inhibitor of several MAPKs, including c-Jun N-terminal kinase. Although, the mechanism by which BRCA1-IRIS overexpression accomplishes that is not yet known, it is sufficient to induce Cyclin D1 overexpression in a human mammary epithelial cell model. Cyclin D1 overexpression could be blocked by co-overexpression of VHR in those cells. Furthermore, in 2 breast cancer cell lines that overexpress both BRCA1-IRIS and Cyclin D1 (MCF-7 and SKBR3) depletion of BRCA1-IRIS by RNA interference attenuated the expression of Cyclin D1 by elevating the expression level of VHR. These data demonstrate a critical role for BRCA1-IRIS in human breast cancer cell-cycle control and suggest that deregulated expression of BRCA1-IRIS is likely to reduce dependence on normal physiological growth stimuli, thereby providing a growth advantage to tumor cells and a potential mechanism of resistance to endocrine therapy. © 2007 Wiley-Liss, Inc. [source] The transcriptional programme of contact-inhibitionJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 5 2010Monika Küppers Abstract Proliferation of non-transformed cells is regulated by cell,cell contacts, which are referred to as contact-inhibition. Vice versa, transformed cells are characterised by a loss of contact-inhibition. Despite its generally accepted importance for cell-cycle control, little is known about the intracellular signalling pathways involved in contact-inhibition. Unravelling the molecular mechanisms of contact-inhibition and its loss during tumourigenesis will be an important step towards the identification of novel target genes in tumour diagnosis and treatment. To better understand the underlying molecular mechanisms we identified the transcriptional programme of contact-inhibition in NIH3T3 fibroblast using high-density microarrays. Setting the cut off: ,1.5-fold, P,,,0.05, 853 genes and 73 cDNA sequences were differentially expressed in confluent compared to exponentially growing cultures. Importing these data into GenMAPP software revealed a comprehensive list of cell-cycle regulatory genes mediating G0/G1 arrest, which was confirmed by RT-PCR and Western blot. In a narrow analysis (cut off: ,2-fold, P,,,0.002), we found 110 transcripts to be differentially expressed representing 107 genes and 3 cDNA sequences involved, for example, in proliferation, signal transduction, transcriptional regulation, cell adhesion and communication. Interestingly, the majority of genes was upregulated indicating that contact-inhibition is not a passive state, but actively induced. Furthermore, we confirmed differential expression of eight genes by semi-quantitative RT-PCR and identified the potential tumour suppressor transforming growth factor-, (TGF-,)-1-induced clone 22 (TSC-22; tgfb1i4) as a novel protein to be induced in contact-inhibited cells. J. Cell. Biochem. 110: 1234,1243, 2010. Published 2010 Wiley-Liss, Inc. [source] Multiple sclerosis in a radiosensitive family with low levels of the ATM proteinJOURNAL OF MEDICAL IMAGING AND RADIATION ONCOLOGY, Issue 3 2002Raymond A Clarke SUMMARY Multiple sclerosis (MS) is a chronic neurological disease of the central nervous system (CNS) characterized by demyelination associated with progressive disability. The mechanisms underlying the pathogenesis of MS remain a mystery. The highly pleiotropic syndrome known as ataxia telangiectasia (A-T) overlaps with MS in that it also presents with demyelination in the CNS. Whether demyelination in MS or in A-T is initiated through neuronal degeneration or immune dysfunction is not yet known. However, unlike MS, the underlying cause of A-T is known to result from mutations in the A,T gene (ATM) that often result in the complete loss of ATM protein and loss/gain of function. ATM is implicated in neurological degeneration, particularly in the cerebellum, cellular apoptosis, immunodeficiency, double stranded deoxyribonucleic acid (DNA) rejoining, VDJ antibody recombination, tumour suppression, particularly T-lymphoid malignancies, signal transduction, cell-cycle control and cellular radiohypersensitivity. In this study, we describe a case of MS in a family with cellular radiosensitivity and abnormally low postinduction levels of the ATM protein. Defective DNA repair/rejoining may impact on autoimmunity. [source] Mutational and expression analysis of CDK1, cyclinA2 and cyclinB1 in epilepsy-associated glioneuronal lesionsNEUROPATHOLOGY & APPLIED NEUROBIOLOGY, Issue 2 2007V. Schick Gangliogliomas and focal cortical dysplasias (FCDs) constitute glioneuronal lesions, which are frequently encountered in biopsy specimens of patients with pharmacoresistant focal epilepsy and relate to impaired differentiation and migration of neural precursors. However, their molecular pathogenesis and relationship are still largely enigmatic. Recent data suggest several components of the insulin-pathway, including TSC1 and TSC2 mutated in tuberous sclerosis complex (TSC), to be altered in gangliogliomas and FCD with Taylor type balloon cells (FCDIIb). The proteins tuberin (TSC2) and hamartin (TSC1) constitute a tumour suppressor mechanism involved in cell-cycle control. Hamartin and/or tuberin were reported to colocalize and/or interact with CDK1, cyclinB1 and cyclinA2 that are critically involved in cell-size and cell-growth control. Here, we have carried out mutational and expression analyses of CDK1, cyclinB1 and cyclinA2 in gangliogliomas and FCDIIb. Mutational screening was performed by single-strand conformation polymorphism analysis in gangliogliomas (n = 20), FCDIIb (n = 35) and controls. CyclinB1 revealed a polymorphism (G to A, cDNA Position 966, GenBank: NM_031966) in exon 7 with similar frequencies in FCDIIb, gangliogliomas and control specimens (FCD n = 9/35; gangliogliomas n = 5/20; control n = 20/100). We used real-time reverse transcription polymerase chain reaction to determine expression levels of CDK1, cyclinB1 and cyclinA2 in 10 FCDIIb and nine gangliogliomas compared with unaffected adjacent control tissue of the same patients. We observed significantly lower expression of CDK1 and cyclinA2 in FCDIIb vs. controls whereas no significant expression differences were present for CDK1, cyclinB1 and cyclinA2 in gangliogliomas. Our data strongly argue against mutational events of CDK1, cyclinB1 and cyclinA2 to play a role in gangliogliomas or FCDIIb. However, a potential functional significance of lower expression for the cell-size and cell-cycle regulators CDK1 and cyclinA2 in FCDIIb composed of large dysplastic neurones and balloon cells needs to be further resolved. [source] Purification, crystallization and preliminary X-ray diffraction analysis of human Gadd45,ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 11 2008Wenzheng Zhang Gadd45, MyD118 and CR6 (also termed Gadd45,, Gadd45, and Gadd45,, respectively) comprise a family of proteins that play important roles in negative growth control, maintenance of genomic stability, DNA repair, cell-cycle control and apoptosis. Recombinant human Gadd45, and its selenomethionine derivative were expressed in an Escherichia coli expression system and purified; they were then crystallized using the hanging-drop vapour-diffusion method. Diffraction-quality crystals were grown at 291,K using PEG 3350 as precipitant. Using synchrotron radiation, the best diffraction data were collected to 2.3,Å resolution for native crystals at 100,K; selenomethionyl derivative data were collected to 3.3,Å resolution. All the crystals belonged to space group I213, with approximate unit-cell parameters a = b = c = 126,Å. [source] | |||||||||||||