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RNA Stability (rna + stability)
Selected AbstractsTrypanosome Alternative Oxidase is Regulated Post-transcriptionally at the Level of RNA StabilityTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 4 2002MINU CHAUDHURI ABSTRACT In the bloodstream form of African trypanosomes, trypanosome alternative oxidase (TAO), the non-cytochrome ubiquinol:oxidoreductase, is the only terminal oxidase of the mitochondrial electron transport system. TAO is developmentally regulated during mitochondrial biogenesis in this parasite. During in vitro differentiation of Trypanosoma bmcei from the bloodstream to the procyclic form, the overall rate of oxygen consumption decreased about 80%. The mode of respiration changed over a 2- to 3-wk period from a cyanide-insensitive, SHAM-sensitive pathway to a predominantly cyanide-sensitive pathway. The TAO protein level gradually decreased to the level present in the procyclic forms during this 3-wk period. However, within the first week of differentiation, the TAO transcript level decreased about 90% and then in the following weeks it reached the level present in the established procyclic form, that is about 20% of that in bloodstream forms. Like other trypanosomatid genes TAO transcript synthesis remains unaltered in fully differentiated bloodstream and procyclic trypanosomes. The half-life of the TAO mRNA was about 3.2 h in the procyclic trypanosomes, whereas the TAO transcript level remained unaltered even after 4 h of incubation with actinomycin D in bloodstream forms. Inhibition of protein synthesis resulted in about a four-fold accumulation of the TAO transcript in the procyclic trypanosomes, comparable to the level present in the bloodstream forms. Thus, TAO is regulated at the level of mRNA stability and de novo protein synthesis is required for the reduction of the TAO mRNA pool in the procyclic form. [source] Evaluation of the use of dried spots and of different storage conditions of plasma for HIV-1 RNA quantificationHIV MEDICINE, Issue 6 2007B Amellal Objectives The aim of the study was to evaluate the use of dried plasma spots to determine HIV-1 RNA viral loads. Methods The viral loads of 30 liquid plasma samples were compared with those of corresponding dried plasma spots on filter paper (DPS-FP) and in tubes (DPS-T), both of which were left for 7 days at 22°C. Also, 10 liquid plasma samples with detectable viral load were stored at 4, 22 or 37°C for 7 days and five further liquid plasma samples were air-dried for up to 54 h to assess the effects of temperature and the drying step on HIV-1 viral load. Results The viral loads of the 30 liquid plasma samples correlated significantly with those of the paired dried spots DPS-FP and DPS-T, but with median losses of 0.64 and 0.69 log10 HIV-1 RNA copies/mL, respectively, and a limit of detection of 3 log10 copies/mL. The 10 liquid plasma samples stored for 1 week at 37°C showed a weaker correlation and had a significantly reduced median viral load (,0.92 log10; P=0.005) when compared with the viral load of the matched plasma stored at ,80°C. Most of the loss happened during the drying step. Conclusions Reliable measurement of HIV-1 RNA viral load requires good plasma storage conditions. HIV RNA stability was affected by desiccation and 1 week of storage at 37°C. However, our findings suggest that liquid plasma can be kept at 4 or 22°C for a week with no effect on viral load. [source] Increased expression of the heterogeneous nuclear ribonucleoprotein K in pancreatic cancer and its association with the mutant p53INTERNATIONAL JOURNAL OF CANCER, Issue 2 2010Renyuan Zhou Abstract The heterogeneous nuclear ribonucleoprotein (hnRNP) K is an essential RNA and DNA binding protein involved in gene expression and signal transduction including DNA transcription, RNA splicing, RNA stability and translation. The role of hnRNP K in cancer is relatively understudied. However, several cellular functions strongly indicate that hnRNP K is involved in tumorigenesis. In this study, we investigated the altered protein expression and the subcellular distribution of the hnRNP K protein using tissue microarrays in pancreatic cancer. We showed an increased cytoplasmic hnRNP K in pancreatic cancer. This increase in hnRNP K protein occurs at the posttranscriptional level. We postulate that the cytoplasmic accumulation of hnRNP K will lead to silenced mRNA translation of tumor suppressor genes and thus contributes to pancreatic cancer development. We also demonstrated that knocking down of hnRNP K expression by siRNA inhibited pancreatic cancer cell growth and colony formation. hnRNP K was identified as a member of the p53/HDM2 pathway. Whether hnRNP K interacts with the mutant p53 is not known. Using two different pancreatic cancer cell lines, we can demonstrate that hnRNP K interacts with the mutant p53. The subcellular distribution and function of the mutant p53 and the interaction of hnRNP K/mutant p53 were affected by the Ras/MEK/ERK pathway, growth factors and the specific p53 mutations in pancreatic cancer cells. Since Kras is activated and p53 is mutated in most pancreatic cancers, these data unveiled an important new signaling pathway that linked by hnRNP K and mutant p53 in pancreatic cancer tumorigenesis. [source] A role for the Escherichia coli H-NS-like protein StpA in OmpF porin expression through modulation of micF RNA stabilityMOLECULAR MICROBIOLOGY, Issue 1 2000Padraig Deighan When a wild-type strain of Escherichia coli and its stpA, hns and stpA hns mutant derivatives were compared by two-dimensional protein gel electrophoresis, the levels of expression of several proteins were found to vary. One of these was identified as the outer membrane porin protein, OmpF. In the stpA hns double mutant, the level of OmpF was downregulated dramatically, whereas in hns or stpA single mutants, it was affected only slightly. Transcription from the ompF promoter was reduced by 64% in the double mutant; however, the level of ompF mRNA was reduced by 96%. This post-transcriptional expression was found to result from a strong reduction in the half-life of ompF message in the double mutant. The micF antisense RNA was shown to be involved in OmpF regulation by StpA using a strain deleted for micF. Moreover, micF antisense RNA accumulated considerably in an stpA hns background. Transcriptional data from a micF,lacZ fusion and measurements of micF RNA half-life confirmed that this was caused by transcriptional derepression of micF as a result of the hns lesion and increased micF RNA stability due to the absence of StpA (a known RNA chaperone). These data suggest a novel facet to the regulation of OmpF expression, namely destabilization of micF RNA by StpA. [source] | |||||||||||||