The Role of Small RNAs and Ribonucleases in the Control of Gene Expression in Salmonella Typhimurium

Dissertation presented to obtain the Ph.D degree in Biology

RNAs are important effectors in the process of gene expression. In bacteria, the levels of the transcripts have to be rapidly adjusted in response to constantly changing environmental demands. The cellular concentration of a given RNA is the result of the balance between its synthesis and degradation. RNA degradation is a complex process encompassing multiple pathways. Ribonucleases are the enzymes that directly process and degrade RNA transcripts, regulating their cellular amounts. The rate at which RNA decay occurs depends on the availability of ribonucleases and their specificities according to the sequence and/or the structural elements of the RNA molecule. Several other factors modulate RNA degradation, namely polyadenylation, which plays a multifunctional role in RNA metabolism. Additionally, small non-coding RNAs are crucial regulators of gene expression, and can directly modulate the stability of their mRNA targets. In many cases this regulation is dependent on Hfq, an RNA binding protein which can act in concert with polyadenylation enzymes and is often necessary for the activity of the sRNAs.(...)