title: Polyadenylation helps regulate functional tRNA levels in Escherichia coli.
abstract: Here we demonstrate a new regulatory mechanism for tRNA processing in Escherichia coli whereby RNase T and RNase PH, the two primary 3' → 5' exonucleases involved in the final step of 3'-end maturation, compete with poly(A) polymerase I (PAP I) for tRNA precursors in wild-type cells. In the absence of both RNase T and RNase PH, there is a >30-fold increase of PAP I-dependent poly(A) tails that are ≤10 nt in length coupled with a 2.3- to 4.2-fold decrease in the level of aminoacylated tRNAs and a >2-fold decrease in growth rate. Only 7 out of 86 tRNAs are not regulated by this mechanism and are also not substrates for RNase T, RNase PH or PAP I. Surprisingly, neither PNPase nor RNase II has any effect on tRNA poly(A) tail length. Our data suggest that the polyadenylation of tRNAs by PAP I likely proceeds in a distributive fashion unlike what is observed with mRNAs.
authors.affiliation: Department of Genetics, University of Georgia, Athens, GA 30602, USA.
authors.forename: Bijoy K
authors.initials: BK
authors.lastname: Mohanty
authors.forename: Valerie F
authors.initials: VF
authors.lastname: Maples
authors.forename: Sidney R
authors.initials: SR
authors.lastname: Kushner
mesh_terms: D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005095:Exoribonucleases / Q000235:genetics; D009154:Mutation; D011061:Poly A / Q000378:metabolism; D026723:Polyadenylation; D011062:Polynucleotide Adenylyltransferase / Q000235:genetics / Q000378:metabolism; D011117:Polyribonucleotide Nucleotidyltransferase / Q000235:genetics; D012322:RNA Precursors / Q000378:metabolism; D012341:RNA, Ribosomal, 5S / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism*; D046249:Transfer RNA Aminoacylation
chemical_list: D029968:Escherichia coli Proteins; D012322:RNA Precursors; D012341:RNA, Ribosomal, 5S; D011061:Poly A; D012343:RNA, Transfer; D011062:Polynucleotide Adenylyltransferase; C063643:pcnB protein, E coli; C056502:ribonuclease PH; D011117:Polyribonucleotide Nucleotidyltransferase; D005095:Exoribonucleases; C042081:exoribonuclease T; C022535:exoribonuclease II