title: Polynucleotide phosphorylase functions both as a 3' right-arrow 5' exonuclease and a poly(A) polymerase in Escherichia coli.
abstract: In vitro, polynucleotide phosphorylase of Escherichia coli can both synthesize RNA by using nucleotide diphosphates as precursors and exonucleolytically degrade RNA in the presence of inorganic phosphate. However, because of the high in vivo concentration of inorganic phosphate in exponentially growing cells, it has been assumed that the enzyme works exclusively as an exonuclease. Here we demonstrate that, contrary to this prediction, polynucleotide phosphorylase not only synthesizes long, highly heteropolymeric tails in vivo, but also accounts for all of the observed residual polyadenylylation in poly(A) polymerase I deficient strains. In addition, the enzyme is responsible for adding the C and U residues that are found in poly(A) tails in exponentially growing cultures of wild type E. coli.
authors.affiliation: Department of Genetics, University of Georgia, Athens, GA 30602-7223, USA.
authors.forename: B K
authors.initials: BK
authors.lastname: Mohanty
authors.forename: S R
authors.initials: SR
authors.lastname: Kushner
mesh_terms: D001483:Base Sequence; D017931:DNA Primers; D004926:Escherichia coli / Q000201:enzymology*; D043211:Exodeoxyribonuclease V; D005090:Exodeoxyribonucleases / Q000378:metabolism*; D009154:Mutation; D011062:Polynucleotide Adenylyltransferase / Q000378:metabolism*; D011117:Polyribonucleotide Nucleotidyltransferase / Q000235:genetics / Q000378:metabolism*; D012316:RNA Nucleotidyltransferases / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; D012333:RNA, Messenger; D012316:RNA Nucleotidyltransferases; C023198:tRNA nucleotidyltransferase; D011062:Polynucleotide Adenylyltransferase; D011117:Polyribonucleotide Nucleotidyltransferase; D005090:Exodeoxyribonucleases; D043211:Exodeoxyribonuclease V