Biology subjects

Barsheshet, M.

Publications and source records attributed to Barsheshet, M..

2 recordsLinked to original sources

bioRxiv2026

A small RNA guides a post-transcriptional regulatory protein to its target

RNA-binding proteins are central to post-transcriptional regulation and are generally thought to recognize their target RNAs through direct binding. Here, we uncover a previously unrecognized mechanism in which a small RNA (sRNA) guides a protein regulator to specific target mRNAs, enabling programmable post-transcriptional control. By mapping in pathogenic Escherichia coli the RNA interactome of CsrA, a global post-transcriptional regulator, we identify ~800 ternary complexes in which CsrA simultaneously binds an sRNA and an mRNA. Focusing on one class of these complexes, we show that PasE, a newly discovered sRNA, directs CsrA to virulence-associated mRNAs that are otherwise not targeted by CsrA, resulting in their repression. Altering the PasE seed sequence redirects CsrA to selected mRNAs, establishing a modular RNA-guided platform for gene regulation. Together, our findings reveal a new and likely widespread mechanism of bacterial post-transcriptional regulation and provide a framework for a new type of RNA-based synthetic regulation.

microbiology↗

bioRxiv2022

Regulation of major bacterial survival strategies by transcript sequestration in a membraneless organelle

Liquid-liquid phase separation (LLPS) of proteins was shown in recent years to regulate spatial organization of cell content without the need for membrane encapsulation in eukaryotes and prokaryotes. Yet evidence for the relevance of LLPS for bacterial cell functionality is largely missing. Here we show that the sugar metabolism-regulating clusters, recently shown by us to assemble in the E. coli cell poles by means of the novel protein TmaR, are formed via LLPS. A mutant screen uncovered residues and motifs in TmaR that are important for its condensation. Upon overexpression, TmaR undergoes irreversible liquid-to-solid transition, similar to the transition of disease-causing proteins in human, which impairs bacterial cell morphology and proliferation. Not only does RNA contribute to TmaR phase separation, but by ensuring polar localization and stability of flagella-related transcripts, TmaR enables cell motility and biofilm formation, thus providing a linkage between LLPS and major survival strategies in bacteria.

microbiology↗