Messenger RNA Turnover Processes in Escherichia coli, Bacillus subtilis, and Emerging Studies in Staphylococcus aureus

Figure 1

Degradosome-mediated RNA decay. The E. coli degradosome is composed of at least four subunits: RNase E, PNPase, RhlB helicase, and enolase. The initial RNA cleavage event is catalyzed by the 5^→3^ endoribonuclease RNase E (large cut-out circle) which loads onto a transcript and scans for downstream cleavage sites: A/U rich regions proceeded by stem-loop structures in 5^ monophosphorylated transcripts. The 3^→5^ exoribonuclease PNPase (small cut-out circle) catalyzes cleavage of RNase E-generated decay intermediates. Otherwise inhibitory secondary structures to PNPase-mediated degradation are resolved by RhlB helicase (cross). The role of enolase (hexagon) in mRNA decay is not well characterized.