title: RNA 3'-tail synthesis in Streptomyces: in vitro and in vivo activities of RNase PH, the SCO3896 gene product and polynucleotide phosphorylase.
abstract: As in other bacteria, 3'-tails are added post-transcriptionally to Streptomyces coelicolor RNA. These tails are heteropolymeric, and although there are several candidates, the enzyme responsible for their synthesis has not been definitively identified. This paper reports on three candidates for this role. First, it is confirmed that the product of S. coelicolor gene SCO3896, although it bears significant sequence similarity to Escherichia coli poly(A) polymerase I, is a tRNA nucleotidyltransferase, not a poly(A) polymerase. It is further shown that SCO2904 encodes an RNase PH homologue that possesses the polymerization and phosphorolysis activities expected for enzymes of that family. S. coelicolor RNase PH can add poly(A) tails to a model RNA transcript in vitro. However, disruption of the RNase PH gene has no effect on RNA 3'-tail length or composition in S. coelicolor; thus, RNase PH does not function as the RNA 3'-polyribonucleotide polymerase [poly(A) polymerase] in that organism. These results strongly suggest that the enzyme responsible for RNA 3'-tail synthesis in S. coelicolor and other streptomycetes is polynucleotide phosphorylase (PNPase). Moreover, this study shows that both PNPase and the product of SCO3896 are essential. It is possible that the dual functions of PNPase in the synthesis and degradation of RNA 3'-tails make it indispensable in Streptomyces.
authors.affiliation: Department of Biology, Emory University, Atlanta, GA 30322, USA.
authors.forename: Patricia
authors.initials: P
authors.lastname: Bralley
authors.affiliation: Department of Molecular Microbiology, The John Innes Centre, Norwich NR4 7UH, UK.
authors.forename: Bertolt
authors.initials: B
authors.lastname: Gust
authors.affiliation: Department of Biology, Emory University, Atlanta, GA 30322, USA.
authors.forename: Samantha
authors.initials: S
authors.lastname: Chang
authors.affiliation: Department of Molecular Microbiology, The John Innes Centre, Norwich NR4 7UH, UK.
authors.forename: Keith F
authors.initials: KF
authors.lastname: Chater
authors.affiliation: Department of Biology, Emory University, Atlanta, GA 30322, USA.
authors.forename: George H
authors.initials: GH
authors.lastname: Jones
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D005095:Exoribonucleases / Q000235:genetics / Q000378:metabolism*; D026723:Polyadenylation; D011117:Polyribonucleotide Nucleotidyltransferase / Q000235:genetics / Q000378:metabolism*; D012316:RNA Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism*; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D012343:RNA, Transfer / Q000235:genetics / Q000378:metabolism; D013302:Streptomyces / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development
chemical_list: D001426:Bacterial Proteins; D012329:RNA, Bacterial; D012343:RNA, Transfer; D012316:RNA Nucleotidyltransferases; C023198:tRNA nucleotidyltransferase; C056502:ribonuclease PH; D011117:Polyribonucleotide Nucleotidyltransferase; D005095:Exoribonucleases