A La Autoantigen Homologue Is Required for the Internal Ribosome Entry Site Mediated Translation of Giardiavirus

Translation of Giardiavirus (GLV) mRNA is initiated at an internal ribosome entry site (IRES) in the viral transcript. The IRES localizes to a downstream portion of 5′ untranslated region (UTR) and a part of the early downstream coding region of the transcript. Recent studies indicated that the IRES does not require a pre-initiation complex to initiate translation but may directly recruit the small ribosome subunit with the help of a number of trans-activating protein factors. A La autoantigen homologue in the viral host Giardia lamblia, GlLa, was proposed as one of the potential trans-activating factors based on its specific binding to GLV-IRES in vitro. In this study, we further elucidated the functional role of GlLa in GLV-IRES mediated translation in Giardia by knocking down GlLa with antisense morpholino oligo, which resulted in a reduction of GLV-IRES activity by 40%. An over-expression of GlLa in Giardia moderately stimulated GLV-IRES activity by 20%. A yeast inhibitory RNA (IRNA), known to bind mammalian and yeast La autoantigen and inhibit Poliovirus and Hepatitis C virus IRES activities in vitro and in vivo, was also found to bind to GlLa protein in vitro and inhibited GLV-IRES function in vivo. The C-terminal domain of La autoantigen interferes with the dimerization of La and inhibits its function. An over-expression of the C-terminal domain (200–348aa) of GlLa in Giardia showed a dominant-negative effect on GLV-IRES activity, suggesting a potential inhibition of GlLa dimerization. HA tagged GlLa protein was detected mainly in the cytoplasm of Giardia, thus supporting a primary role of GlLa in translation initiation in Giardiavirus

First Report of Circulating MicroRNAs in Tumour Necrosis Factor Receptor-Associated Periodic Syndrome (TRAPS)

Tumor necrosis factor-receptor associated periodic syndrome (TRAPS) is a rare autosomal dominant autoinflammatory disorder characterized by recurrent episodes of long-lasting fever and inflammation in different regions of the body, such as the musculo-skeletal system, skin, gastrointestinal tract, serosal membranes and eye. Our aims were to evaluate circulating microRNAs (miRNAs) levels in patients with TRAPS, in comparison to controls without inflammatory diseases, and to correlate their levels with parameters of disease activity and/or disease severity. Expression levels of circulating miRNAs were measured by Agilent microarrays in 29 serum samples from 15 TRAPS patients carrying mutations known to be associated with high disease penetrance and from 8 controls without inflammatory diseases. Differentially expressed and clinically relevant miRNAs were detected using GeneSpring GX software. We identified a 6 miRNAs signature able to discriminate TRAPS from controls. Moreover, 4 miRNAs were differentially expressed between patients treated with the interleukin (IL)-1 receptor antagonist, anakinra, and untreated patients. Of these, miR-92a-3p and miR-150-3p expression was found to be significantly reduced in untreated patients, while their expression levels were similar to controls in samples obtained during anakinra treatment. MiR-92b levels were inversely correlated with the number of fever attacks/year during the 1st year from the index attack of TRAPS, while miR-377-5p levels were positively correlated with serum amyloid A (SAA) circulating levels. Our data suggest that serum miRNA levels show a baseline pattern in TRAPS, and may serve as potential markers of response to therapeutic intervention

The RNA binding protein HuR differentially regulates unique subsets of mRNAs in estrogen receptor negative and estrogen receptor positive breast cancer

<p>Abstract</p> <p>Background</p> <p>The discordance between steady-state levels of mRNAs and protein has been attributed to posttranscriptional control mechanisms affecting mRNA stability and translation. Traditional methods of genome wide microarray analysis, profiling steady-state levels of mRNA, may miss important mRNA targets owing to significant posttranscriptional gene regulation by RNA binding proteins (RBPs).</p> <p>Methods</p> <p>The ribonomic approach, utilizing RNA immunoprecipitation hybridized to microarray (RIP-Chip), provides global identification of putative endogenous mRNA targets of different RBPs. HuR is an RBP that binds to the AU-rich elements (ARE) of labile mRNAs, such as proto-oncogenes, facilitating their translation into protein. HuR has been shown to play a role in cancer progression and elevated levels of cytoplasmic HuR directly correlate with increased invasiveness and poor prognosis for many cancers, including those of the breast. HuR has been described to control genes in several of the acquired capabilities of cancer and has been hypothesized to be a tumor-maintenance gene, allowing for cancers to proliferate once they are established.</p> <p>Results</p> <p>We used HuR RIP-Chip as a comprehensive and systematic method to survey breast cancer target genes in both MCF-7 (estrogen receptor positive, ER+) and MDA-MB-231 (estrogen receptor negative, ER-) breast cancer cell lines. We identified unique subsets of HuR-associated mRNAs found individually or in both cell types. Two novel HuR targets, <it>CD9 </it>and <it>CALM2 </it>mRNAs, were identified and validated by quantitative RT-PCR and biotin pull-down analysis.</p> <p>Conclusion</p> <p>This is the first report of a side-by-side genome-wide comparison of HuR-associated targets in wild type ER+ and ER- breast cancer. We found distinct, differentially expressed subsets of cancer related genes in ER+ and ER- breast cancer cell lines, and noted that the differential regulation of two cancer-related genes by HuR was contingent upon the cellular environment.</p

An update on the use of animal models in diabetic nephropathy research

In the current review, we discuss limitations and recent advances in animal models of diabetic nephropathy (DN). As in human disease, genetic factors may determine disease severity with the murine FVB and DBA/2J strains being more susceptible to DN than C57BL/6J mice. On the black and tan, brachyuric (BTBR) background, leptin deficient (ob/ob) mice develop many of the pathological features of human DN. Hypertension synergises with hyperglycemia to promote nephropathy in rodents. Moderately hypertensive endothelial nitric oxide synthase (eNOS(−/−)) deficient diabetic mice develop hyaline arteriosclerosis and nodular glomerulosclerosis and induction of renin-dependent hypertension in diabetic Cyp1a1mRen2 rats mimics moderately severe human DN. In addition, diabetic eNOS(−/−) mice and Cyp1a1mRen2 rats recapitulate many of the molecular pathways activated in the human diabetic kidney. However, no model exhibits all the features of human DN; therefore, researchers should consider biochemical, pathological, and transcriptomic data in selecting the most appropriate model to study their molecules and pathways of interest

BCR/ABL activates mdm2 rnRNA translation via the La antigen

In a BCR/ABL-expressing myeloid precursor cell line, p53 levels were markedly downmodulated. Expression of MDM2, the negative regulator of p53, was upregulated in a tyrosine kinase-dependent manner in growth factor-independent BCR/ABL-expressing cells, and in accelerated phase and blast crisis CML samples. Increased MDM2 expression was associated with enhanced mdm2 mRNA translation, which required the interaction of the La antigen with mdm2 5' UTR. Expression of MDM2 correlated with that of La and was suppressed by La siRNAs and by a dominant negative La mutant, which also enhanced the susceptibility to drug-induced apoptosis of BCR/ABL-transformed cells. By contrast, La overexpression led to increased MDM2 levels and enhanced resistance to apoptosis. Thus, La-dependent activation of mdm2 translation might represent an important molecular mechanism involved in BCR/ABL leukemogenesis

A La protein requirement for efficient pre-tRNA folding

The La protein protects the 3′ ends of many nascent small RNAs from exonucleases. Here we report that La is required for efficient folding of certain pre-tRNAs. A mutation in pre-tRNA(Arg)(CCG) causes yeast cells to be cold-sensitive and to require the La protein Lhp1p for efficient growth. When the mutant cells are grown at low temperature, or when Lhp1p is depleted, mature tRNA(Arg)(CCG) is not efficiently aminoacylated. The mutation causes the anticodon stem of pre-tRNA(Arg)(CCG) to misfold into an alternative helix in vitro. Intragenic suppressor mutations that disrupt the misfolded helix or strengthen the correct helix alleviate the requirement for Lhp1p, providing evidence that the anticodon stem misfolds in vivo. Chemical and enzymatic footprinting experiments suggest a model in which Lhp1p stabilizes the correctly folded stem. Lhp1p is also required for efficient aminoacylation of two wild-type tRNAs when yeast are grown at low temperature. These experiments reveal that pre-tRNAs can require protein assistance for efficient folding in vivo