title: Functional overlap of tRNA nucleotidyltransferase, poly(A) polymerase I, and polynucleotide phosphorylase.
abstract: Repair of the 3'-terminal -CCA sequence of tRNA generally requires the action of the enzyme tRNA nucleotidyltransferase. However, in Escherichia coli in the absence of this enzyme, a decreased level of tRNA end repair continues. To ascertain the enzymes responsible for this residual repair, mutant strains were constructed lacking tRNA nucleotidyltransferase and other enzymes potentially involved in the process, poly(A) polymerase I and polynucleotide phosphorylase (PNPase). Strains lacking tRNA nucleotidyltransferase and either one of the other enzymes displayed decreased growth rates and increased levels of defective tRNA compared with the single cca mutant. Triple mutants lacking all three enzymes grew very slowly, had even more defective tRNA, and were devoid of activity incorporating AMP into tRNA-C-C. Overexpression of poly(A) polymerase I, but not PNPase, partially compensated for the absence of tRNA nucleotidyltransferase. These data show that poly(A) polymerase I and PNPase participate in the end repair process and are required to maintain functional tRNA levels when tRNA nucleotidyltransferase is absent.
authors.affiliation: Department of Biochemistry,University of Connecticut Health Center, Farmington, Connecticut 06030, USA.
authors.forename: N B
authors.initials: NB
authors.lastname: Reuven
authors.forename: Z
authors.initials: Z
authors.lastname: Zhou
authors.forename: M P
authors.initials: MP
authors.lastname: Deutscher
mesh_terms: D000249:Adenosine Monophosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D015152:Blotting, Northern; D004260:DNA Repair; D004926:Escherichia coli; D029968:Escherichia coli Proteins; D011062:Polynucleotide Adenylyltransferase; D011117:Polyribonucleotide Nucleotidyltransferase / Q000378:metabolism*; D012316:RNA Nucleotidyltransferases / Q000378:metabolism*; D012343:RNA, Transfer / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D000249:Adenosine Monophosphate; D012343:RNA, Transfer; D012316:RNA Nucleotidyltransferases; C023198:tRNA nucleotidyltransferase; D011062:Polynucleotide Adenylyltransferase; C063643:pcnB protein, E coli; D011117:Polyribonucleotide Nucleotidyltransferase