Structure and function of RNase AS: A novel virulence factor from mycobacterium tuberculosis

The 3'-ends of both prokaryotic and eukaryotic RNA can be polyadenylated and the effect of polyadenylation is known to increase the stability of transcripts in eukaryotes, whereas it promotes instability in prokaryotes. RNAs are considered as key effectors of virulence mechanisms, since they are directly involved in regulatory pathways in pathogenic bacteria. Deadenylation of RNA is thus an important control point and rate-limiting step of its turnover. RNase AS is a novel identified protein of Mycobacterium tuberculosis, which dramatically hampers mycobacterial virulence in vivo, with a mechanism which is still to be fully defined. Phylogenetic analysis identifies orthologs of RNase AS in all mycobacteria. However, functional data only recently clarified that RNase AS is an exo-ribonuclease, which is highly specific in degrading polyadenylate sequences of RNA. This Review summarizes the current knowledge on structure and function of RNase AS and underscores its role in the process of RNA maturation. An overall description of all mycobacterial ribonucleases hitherto characterized is also provided.