The RNA chaperone Hfq is an important bacterial post-transcriptional regulator. Most studies on Hfq are focused on the role of this protein on small non-coding RNAs (sRNAs) and messenger RNAs (mRNAs). The most well-characterized function of Hfq is its role as RNA matchmaker, promoting the base-pairing between sRNAs and their mRNA targets. However, novel substrates and previous unrecognized functions of Hfq have now been identified, which expanded the regulatory spectrum of this protein. Hfq was recently found to bind rRNA and act as a new ribosome biogenesis factor, affecting rRNA processing, ribosome assembly, translational efficiency and translational fidelity. Hfq was also found to bind tRNAs, which could provide an additional mechanism for its role on the accuracy of protein synthesis. The list of substrates does not include RNA exclusively since Hfq was shown to bind DNA, playing an important role in DNA compaction. Additionally, Hfq is also capable to establish many protein-protein interactions. Overall, the functions of the RNA-binding protein Hfq have been expanded beyond its function in small RNA-mediated regulation. The identification of additional substrates and new functions provides alternative explanations for the importance of the chaperone Hfq as a global regulator.
Keywords: DNA; Hfq; Lsm family; Post-transcriptional regulation; mRNA; rRNA; sRNA; tRNA.