NEW INSIGHTS ON RIBOSOME BIOGENESIS: THE CRITICAL ROLE OF HFQ AND RNASE R ON RRNA QUALITY CONTROL

• Autor(a) principal: Santos, Ricardo Filipe da Cruz Duarte dos
• Data de Publicação: 2013
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/147725
• topic: Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

RNase R and Hfq are two important proteins that are implicated in post-transcrip-tional gene expression that also integrate the bacterial RNA degradation mechanisms. RNase R is known to preferably bind to polyadenylated 3’-end tails of RNAs besides being also capable of degrading structured RNA molecules. Hfq also preferably binds to polyadenylated stretches near structured RNA regions. The apparent sharing of substrates has prompted us to further investigate the role of both these proteins in RNA degradation. In this work we have found evidence of a possible functional cooperation between RNase R and Hfq. Cells lacking these proteins were found to accumulate products of ribosomal RNA degradation. Our data also indicates accumulation of rRNA precursors of the 16S, 23S and 5S ribosomal RNAs, yielding immature RNA molecules. The ribo-somal biogenesis is a complex and precise process by which the ribosomes are generated and assembled. Our data evidences drastic defects in ribosomal biogenesis when both Hfq and RNase R are absent. In the Δhfq Δrnr double mutant, ribosomal profiles are shown to be defective as the amount of 70S particles in this mutant is lowered. The synergetic role between this proteins is further supported by our data concerning protein interaction assays. Here we have shown that RNase R and Hfq interact directly with each other, which nicely expands the interaction network of both these proteins. Taken all together, we provide evidence of a possible new RNA degradation pathway that imply the cooper-ative action of both the exoribonuclease RNase R and the RNA chaperone Hfq and that RNase R was found to be the major exoribonuclease for the removal of accumulated rRNA fragments in the absence of Hfq.