Tyrosine phosphorylation controlled poly(A) polymerase I activity regulates general stress response in bacteria

Abstract

RNA 3′-end polyadenylation that marks transcripts for degradation is implicated in general stress response inEscherichia coli. Yet, the mechanism and regulation of poly(A) polymerase I (PAPI) in stress response are obscure. We show thatpcnB(that encodes PAPI)-null mutation widely stabilises stress response mRNAs and imparts cellular tolerance to multiple stresses, whereas PAPI ectopic expression renders cells stress-sensitive. We demonstrate that there is a substantial loss of PAPI activity on stress exposure that functionally phenocopiespcnB-null mutation stabilising target mRNAs. We identify PAPI tyrosine phosphorylation at the 202 residue (Y202) that is enormously enhanced on stress exposure. This phosphorylation inhibits PAPI polyadenylation activity under stress. Consequentially, PAPI phosphodeficient mutation (tyrosine 202 to phenylalanine, Y202F) fails to stimulate mRNA expression rendering cells stress-sensitive. Bacterial tyrosine kinase Wzc phosphorylates PAPI-Y202 residue, and thatwzc-null mutation renders cells stress-sensitive. Accordingly,wzc-null mutation has no effect on stress sensitivity in the presence ofpcnB-null orpcnB-Y202Fmutation. We also establish that PAPI phosphorylation-dependent stress tolerance mechanism is distinct and operates downstream of the primary stress regulator RpoS.