mRNA Degradation Pathways in E. coli

mRNA degradation is an essential process that couples transcription and translation in bacterial fate and plays an important part in gene expression dynamics. RNase E serves as the key regulator in mRNA degradation pathways in E. coli. The traditional view that RNase E-mediated endonucleolytic cleavage is the primary step has been extended by the discovery that the enzyme's activity is critically governed by the phosphorylation state of the mRNA 5'-terminus. Specifically, triphosphorylated primary transcripts require pyrophosphate removal by the pyrophosphohydrolase RppH, which forms a heterotetrameric complex with DapF (an enzyme essential for lysine and peptidoglycan biosynthesis), to generate a 5'-monophosphorylated substrate. RNase E exhibits significantly higher affinity for these monophosphorylated ends, thereby facilitating efficient recruitment and subsequent exonucleolytic digestion. Consequently, in this 5'-end-dependent pathway, the RppHcatalyzed conversion, rather than the RNase E cleavage itself, is the initial and ratedetermining step. In this review, we summarize the mechanisms of mRNA decay pathways in E. coli, detailing the roles of various enzymes involved in 5'-end-dependent pathway and discuss the potential moonlighting roles of metabolic enzymes in regulating mRNA stability.