Identification of MazF Homologue in Legionella pneumophila Which Cleaves RNA at the AACU Sequence

Abstract

MazF is a sequence-specific endoribonuclease that is widely conserved in bacteria and archaea. Here, we found an MazF homologue (MazF-lp; LPO-p0114) in <i>Legionella pneumophila</i>.<i></i> The<i> mazF-lp</i> gene overlaps 14 base pairs with the upstream gene<i> mazE-lp</i> (MazE-lp; LPO-p0115). The induction of <i>mazF-lp</i> caused cell growth arrest, while <i>mazE-lp</i> co-induction recovered cell growth in <i>Escherichia coli</i>. In vivo<i></i> and<i></i> in vitro primer extension experiments showed that MazF-lp is a sequence-specific endoribonuclease cleaving RNA at AACU. The endoribonuclease activity of purified MazF-lp was inhibited by purified MazE-lp. We found that MazE-lp and the MazEF-lp complex specifically bind to the palindromic sequence present in the 5′-untranslated region of the <i>mazEF-lp</i> operon. MazE-lp and MazEF-lp both likely function as a repressor for the <i>mazEF-lp</i> operon and for other genes, including <i>icmR</i>, whose gene product functions as a secretion chaperone for the IcmQ pore-forming protein, by specifically binding to the palindromic sequence in 5′-UTR of these genes.