Understanding the importance of C-terminal Domain of Hfq in sRNA-release and turnover

Abstract

Acinetobacter baumannii is an opportunistic nosocomial pathogen. This bacterium exhibits a high level of genetic plasticity that potentiates its survival within the host and helps in establishing successful infections. Small regulatory RNA-mediated post-transcriptional regulation of genes is an important cog in the highly plastic genetic machinery of this bacterium. Such regulations are mediated by a global RNA chaperone protein termed Hfq. Hfq mediates sRNA-mRNA interaction by bringing the interacting partners into close proximity with the help of an Sm-like domain that is conserved pan-genera. In A. baumannii, however, the Hfq possesses an extensively long C-terminal domain which is unique to this bacterium. The exact role of this unique CTD of A. baumannii in mediating sRNA-mRNA interaction is not yet studied. Moreover, the CTD of A. baumannii Hfq is composed of multiple “GGQGGF” amino acid repeats. Its CTD is extensively long, 96 amino acids in length, and is composed of “GGQGGF” amino acid residues repeated in tandem. Two critical questions arise from these observations. Firstly, whether the “GGQGGF repeats are redundant in nature, and secondly, how does this uniquely long CTD help in RNA turnover. Thus, these unique structural aspects of A. baumannii Hfq make it an important area for investigation. This raises the question of whether the recurring “GGQGGF” sequences are an evolutionary artefact or are they essential in mediating sRNA-mRNA interaction. Thus, the aim of this study is to understand the biophysical significance of “GGQGGF” repeats in A. baumannii Hfq and how it helps in sRNA-mRNA interaction.