Regulating with ribonucleases in Streptococcus pyogenes

Laura Broglia, Humboldt-Universität Zu Berlin
Bacteria have developed a plethora of strategies to cope with constantly changing environmental conditions, including post-transcriptional regulatory mechanisms. With this regard, regulation of gene expression can be achieved by either the rapid removal or stabilization of RNA molecules by ribonucleases (RNases). RNases exhibit species-specific effects on gene expression, bacterial physiology and different strategies of target recognition, indicating that our understanding of the RNA
more » ... the RNA degradation machinery is not yet complete. The aim of this thesis was to investigate the features and functions of endoRNase Y from the strict human pathogen Streptococcus pyogenes. To gain insight into the role and specificity of this RNase, we identified RNase Y cleavage positions (i.e. targetome) genome-wide by RNA sequencing. Next, to investigate the RNA degradation pathway depending on RNase Y, we compared the RNase Y targetome with the ones of the three 3′-to-5′ exoribonuclease (exoRNases), namely PNPase, YhaM and RNase R. Finally, to dissect the requirements for RNase Y processing and to decipher the role of RNase Y in virulence gene regulation, we studied the impact of RNase Y on speB mRNA, encoding a major virulence factor. This study reveals that RNase Y preferentially cleaves RNAs downstream of a guanosine and for the first time we were able to show that the presence of a guanosine residue is essential for the processing of speB mRNA, in vivo. Although RNase Y cleaves the speB mRNA, our data underpin a model in which RNase Y-mediated regulation of speB expression occurs at the transcriptional level. Using the targetome comparative approach, we demonstrated that RNase Y initiates RNA decay in S. pyogenes and that the RNase Y-generated RNA 3′ ends are usually further trimmed by PNPase and/or YhaM. Overall, these findings increase our understanding of RNase Y functionality and RNA degradation in Gram-positive bacteria.
doi:10.18452/21573 fatcat:qbd6ggqqnrdyjjapg355v5kere