RNase E and the High-Fidelity Orchestration of RNA Metabolism.

The bacterial endoribonuclease RNase E occupies a pivotal position in the control of gene expression, as its actions either commit transcripts to an irreversible fate of rapid destruction or unveil their hidden functions through specific processing. Moreover, the enzyme contributes to quality control of rRNAs. The activity of RNase E can be directed and modulated by signals provided through regulatory RNAs that guide the enzyme to specific transcripts that are to be silenced. Early in its evolutionary history, RNase E acquired a natively unfolded appendage that recruits accessory proteins and RNA. These accessory factors facilitate the activity of RNase E and include helicases that remodel RNA and RNA-protein complexes, and polynucleotide phosphorylase, a relative of the archaeal and eukaryotic exosomes. RNase E also associates with enzymes from central metabolism, such as enolase and aconitase. RNase E-based complexes are diverse in composition, but generally bear mechanistic parallels with eukaryotic machinery involved in RNA-induced gene regulation and transcript quality control. That these similar processes arose independently underscores the universality of RNA-based regulation in life. Here we provide a synopsis and perspective of the contributions made by RNase E to sustain robust gene regulation with speed and accuracy.Wellcome Trus

Suppressor of clathrin deficiency (Scd6)An emerging RGG-motif translation repressor

Translation control plays a key role in variety of cellular processes. Translation initiation factors augment translation, whereas translation repressor proteins inhibit translation. Different repressors act by distinct mechanisms to accomplish the repression process. Although messenger RNAs (mRNAs) can be repressed at various steps of translation, most repressors have been reported to target the initiation step. We focus on one such translation repressor, an Arginine-Glycine-Glycine (RGG)-motif containing protein Scd6. Using this protein as a model, we present a discourse on the known and possible functions of this repressor, its mechanism of action and its recently reported regulation. We suggest a case for conservation of the mechanism employed by Scd6 along with its regulation in orthologs, and propose that Scd6 family of proteins will be an ideal tool to understand translation control and mRNA fate decision mechanisms across biological systems. This article is categorized under: Translation > Translation Regulation RNA Turnover and Surveillance > Turnover/Surveillance Mechanisms RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexe

PSP2 , a gene encoding RGG-motif protein, is a novel suppressor of clathrin heavy chain deficiency

Abstract Clathrin, made up of the heavy- and light-chains, constitutes one of the most abundant protein in vesicles involved in intracellular protein trafficking and endocytosis. YPR129W, which encodes RGG-motif containing translation repressor was identified as a part of multi-gene construct (SCD6) that suppressed clathrin deficiency. However, the contribution of YPR129W alone in suppressing clathrin deficiency has not been documented. In this study we identify YPR129W as a necessary and sufficient gene in a multigene construct SCD6 that suppresses clathrin deficiency. Importantly, we identify cytoplasmic RGG-motif protein encoding gene PSP2 as a novel suppressor of clathrin deficiency. Three other RGG-motif protein encoding genes SBP1, DED1 and GBP2 do not suppress clathrin deficiency. DHH1, a DEAD-box RNA helicase with translation repression activity also fails to rescue clathrin deficiency. α-factor secretion assay suggests that suppression of clathrin deficiency by SCD6 and PSP2 is not mediated by the rescue of the trans-Golgi network (TGN) protein sorting defect observed in the absence of CHC1. Detailed domain analysis of the two suppressors reveals that the RGG-motif of both Scd6 and Psp2 is important for suppressing clathrin deficiency. Additionally, the Lsm domain deletion as well as the arginine to alanine mutation in the arginine methylation defective (AMD) mutant render Scd6 defective in suppressing clathrin deficiency. Overall based on our results using SCD6 and PSP2 proteins, we identify a novel role of RGG-motif in suppressing clathrin deficiency. Since both the suppressors are RNA-binding granule-resident proteins, this study opens an exciting avenue for exploring the connection between clathrin function and cytoplasmic RNA metabolism.</jats:p