The polyadenlyate binding protein (PABP) and translational control /

Translation is the process by which proteins are synthesized from messenger RNAs. This complex process is regulated by a multitude of factors (1). One such factor is the Polyadenylate Binding Protein (PABP), an abundant protein associated with messenger ribonucleoprotein particles (mRNPs) (18). As a result of its interaction with both poly(A) RNA and eukaryotic initiation factor 4G (eIF4G), a component of the tripartite eIF4F cap-binding complex, PABP elicits mRNA circularization and stimulates translation (2). Although the mechanism by which mRNA circularization facilitates translation is not clear, one model suggests that circularization promotes ribosome recycling. Recently, an interaction between PABP and the termination factor, eukaryotic Release Factor3 (eRF3/GSPT) was demonstrated in mammals (71). By interacting with both eRF3 and eIF4G, it was postulated that PABP physically bridges the stop codon to the 5' cap structure, enabling terminating ribosomes to reinitiate translation on the same mRNA. To explore this idea, several PABP mutants lacking the ability to bind eRF3 were generated and added to a PABP-depleted Krebs-2 Cell-Free Extract to study the effects on translation. The PABP mutants stimulated translation as effectively as wild-type PABP, suggesting that the eRF3-PABP interaction is dispensable for translation and ribosome recycling. RNA-binding protein localization may be regulated by methylation and protein-protein interactions (98). PABP was also recently identified as a Coactivator-Associated Arginine Methyltransferase I (CARMI) substrate (23). Here, we show that PABP methylation does not modulate nuclear shuttling or its interactions with 14-3-3, a novel PABP-interacting protein. Translation in "non-nuclear" rabbit reticulocyte lysate is robust and PABP-independent, suggesting a loss of inhibitory control by nuclear factors. We reveal for the first time that the general RNA-binding protein YB-1 renders translation i

General RNA-binding proteins have a function in poly(A)-binding protein-dependent translation

The interaction between the poly(A)-binding protein (PABP) and eukaryotic translational initiation factor 4G (eIF4G), which brings about circularization of the mRNA, stimulates translation. General RNA-binding proteins affect translation, but their role in mRNA circularization has not been studied before. Here, we demonstrate that the major mRNA ribonucleoprotein YB-1 has a pivotal function in the regulation of eIF4F activity by PABP. In cell extracts, the addition of YB-1 exacerbated the inhibition of 80S ribosome initiation complex formation by PABP depletion. Rabbit reticulocyte lysate in which PABP weakly stimulates translation is rendered PABP-dependent after the addition of YB-1. In this system, eIF4E binding to the cap structure is inhibited by YB-1 and stimulated by a nonspecific RNA. Significantly, adding PABP back to the depleted lysate stimulated eIF4E binding to the cap structure more potently if this binding had been downregulated by YB-1. Conversely, adding nonspecific RNA abrogated PABP stimulation of eIF4E binding. These data strongly suggest that competition between YB-1 and eIF4G for mRNA binding is required for efficient stimulation of eIF4F activity by PABP

Enhanced infection prophylaxis reduces mortality in severely immunosuppressed HIV-infected adults and older children initiating antiretroviral therapy in Kenya, Malawi, Uganda and Zimbabwe: the REALITY trial

Meeting abstract FRAB0101LB from 21st International AIDS Conference 18–22 July 2016, Durban, South Africa. Introduction: Mortality from infections is high in the first 6 months of antiretroviral therapy (ART) among HIV‐infected adults and children with advanced disease in sub‐Saharan Africa. Whether an enhanced package of infection prophylaxis at ART initiation would reduce mortality is unknown. Methods: The REALITY 2×2×2 factorial open‐label trial (ISRCTN43622374) randomized ART‐naïve HIV‐infected adults and children >5 years with CD4 <100 cells/mm3. This randomization compared initiating ART with enhanced prophylaxis (continuous cotrimoxazole plus 12 weeks isoniazid/pyridoxine (anti‐tuberculosis) and fluconazole (anti‐cryptococcal/candida), 5 days azithromycin (anti‐bacterial/protozoal) and single‐dose albendazole (anti‐helminth)), versus standard‐of‐care cotrimoxazole. Isoniazid/pyridoxine/cotrimoxazole was formulated as a scored fixed‐dose combination. Two other randomizations investigated 12‐week adjunctive raltegravir or supplementary food. The primary endpoint was 24‐week mortality. Results: 1805 eligible adults (n = 1733; 96.0%) and children/adolescents (n = 72; 4.0%) (median 36 years; 53.2% male) were randomized to enhanced (n = 906) or standard prophylaxis (n = 899) and followed for 48 weeks (3.8% loss‐to‐follow‐up). Median baseline CD4 was 36 cells/mm3 (IQR: 16–62) but 47.3% were WHO Stage 1/2. 80 (8.9%) enhanced versus 108(12.2%) standard prophylaxis died before 24 weeks (adjusted hazard ratio (aHR) = 0.73 (95% CI: 0.54–0.97) p = 0.03; Figure 1) and 98(11.0%) versus 127(14.4%) respectively died before 48 weeks (aHR = 0.75 (0.58–0.98) p = 0.04), with no evidence of interaction with the two other randomizations (p > 0.8). Enhanced prophylaxis significantly reduced incidence of tuberculosis (p = 0.02), cryptococcal disease (p = 0.01), oral/oesophageal candidiasis (p = 0.02), deaths of unknown cause (p = 0.02) and (marginally) hospitalisations (p = 0.06) but not presumed severe bacterial infections (p = 0.38). Serious and grade 4 adverse events were marginally less common with enhanced prophylaxis (p = 0.06). CD4 increases and VL suppression were similar between groups (p > 0.2). Conclusions: Enhanced infection prophylaxis at ART initiation reduces early mortality by 25% among HIV‐infected adults and children with advanced disease. The pill burden did not adversely affect VL suppression. Policy makers should consider adopting and implementing this low‐cost broad infection prevention package which could save 3.3 lives for every 100 individuals treated