title: Initiation of RNA decay in Escherichia coli by 5' pyrophosphate removal.
abstract: The common belief that endonucleolytic cleavage is the initial, rate-determining step of mRNA decay in Escherichia coli fails to explain the influence of 5' termini on the half-lives of primary transcripts. We have re-examined the initial events of RNA degradation in that organism by devising an assay to probe the 5' phosphorylation state of RNA and by employing a self-cleaving hammerhead ribozyme to investigate the degradative consequences of an unphosphorylated 5' end. These studies have identified a previously unrecognized prior step in decay that triggers subsequent internal cleavage by the endonuclease RNase E and thereby governs RNA longevity: the rate-determining conversion of a triphosphorylated to a monophosphorylated 5' terminus. Our findings redefine the role of RNase E in RNA degradation and explain how unpaired 5'-terminal nucleotides can facilitate access to internal cleavage sites within primary transcripts. Moreover, these results reveal a striking parallel between the mechanisms of mRNA decay in prokaryotic and eukaryotic organisms.
authors.affiliation: Kimmel Center for Biology and Medicine at the Skirball Institute, New York University School of Medicine, New York, NY 10016, USA.
authors.forename: Helena
authors.initials: H
authors.lastname: Celesnik
authors.forename: Atilio
authors.initials: A
authors.lastname: Deana
authors.forename: Joel G
authors.initials: JG
authors.lastname: Belasco
mesh_terms: D001483:Base Sequence; D011756:Diphosphates / Q000302:isolation & purification / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics*; D017665:Hydroxyl Radical; D008954:Models, Biological; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010766:Phosphorylation; D020871:RNA Stability; D012329:RNA, Bacterial / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D011756:Diphosphates; D012329:RNA, Bacterial; D012333:RNA, Messenger; D017665:Hydroxyl Radical