Bacteriophage T7 protein kinase phosphorylates RNase E and stabilizes mRNAs synthesized by T7 RNA polymerase.
The T7 protein encoded by the early gene 0.7 exhibits bifunctional activity. Whereas its C-terminal one-third participates in host transcription shut-off, the N-terminal two-thirds bears a protein kinase ('PK') activity that can phosphorylate a number of host proteins in addition to itself. Here, we show that, when PK is expressed in uninfected Escherichia coli cells, the C-terminal half of RNase E and the associated RNA helicase RhlB are heavily phosphorylated. Meanwhile, a subset of RNase E substrates, including the lac and cat mRNAs synthesized by bacteriophage T7 RNA polymerase (RNAP), are stabilized. These mRNAs are genuinely less stable than their counterparts synthesized by E. coli RNAP, because T7 RNAP outpaces translating ribosomes, creating naked, RNase E-sensitive mRNA stretches behind itself. Thus, PK alleviates this effect of desynchronizing transcription and translation. The relationship between the modification of RNase E and RhlB and these mRNA stabilization effects, which may be relevant to the stability of late T7 mRNAs during infection, is discussed.
Marchand
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Laboratoire de Génétique Moléculaire (CNRS UMR 8541), ENS, 46 rue d'Ulm, 75230 Paris, France.
Nicholson
A W
AW
Dreyfus
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M
D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004722:Endoribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000254:growth & development / Q000378:metabolism / Q000821:virology; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D020871:RNA Stability; D012333:RNA, Messenger / Q000378:metabolism*; D013604:T-Phages / Q000201:enzymology* / Q000472:pathogenicity / Q000502:physiology; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
D012333:RNA, Messenger; D014764:Viral Proteins; C072445:0.7 protein, Enterobacteria phage T7; D017346:Protein Serine-Threonine Kinases; C062210:bacteriophage T7 RNA polymerase; D012321:DNA-Directed RNA Polymerases; D004722:Endoribonucleases; C022537:ribonuclease E