Acetylation regulates the oligomerization state and activity of RNase J, the major ribonuclease of Helicobacter pylori

In the pathogenic bacterium Helicobacter pylori, post-transcriptional regulation is dominated by the activity of a protein complex, known as the RNA degradosome, composed of the essential ribonuclease RNase J and the DEAD-box RNA helicase RhpA. Here, we describe post-translational modifications of this protein complex that affect its activity. Cell-extracted RNase J is acetylated on multiple residues, one of which, K649, impacts strongly on RNase J oligomerization, which in turn influences recruitment into the degradosome and ribonuclease activity. Corroborating the link between oligomerization and activity, mutations targeting K649 and other residues affect the dimerization and in vitro activity of RNase J. Our crystal structure of RNase J reveals loops that gate access to the active site and rationalizes how oligomerization state influences activity. We show that the acetylated residues of RNase J are important for H. pylori morphology, highlighting that the modifications affect the cellular function of RNase J. We propose acetylation as a regulatory level controlling the activity of RNase J and the H. pylori RNA degradosome.