mRNAs can be stabilized by DEAD-box proteins.
Eubacterial messenger RNAs are synthesized and translated simultaneously; moreover the speed of ribosomes usually matches that of RNA polymerase. We report here that when in Escherichia coli the host RNA polymerase is replaced by the eightfold faster bacteriophage T7 enzyme for the transcription of the lacZ gene, the beta-galactosidase yield per transcript is depressed 100-fold. But the overexpression of DEAD-box proteins greatly improves this low yield by stabilizing the corresponding transcripts. More generally, it stabilizes inefficiently translated E. coli mRNAs. Ribosome-free mRNA regions, such as those lying behind the fast T7 enzyme or between successive ribosomes on inefficiently translated transcripts, are often unstable and we propose that DEAD-box proteins protect them from endonucleases. These results pinpoint the importance of transcription-translation synchronization for mRNA stability, and reveal an undocumented property of DEAD-box RNA helicases. These proteins have been implicated in a variety of processes involving RNA but not mRNA stability.
Iost
I
I
Laboratoire de Génétique Moléculaire (CNRS D1302), Ecole Normale Supérieure, Paris, France.
Dreyfus
M
M
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000502:physiology*; D017123:Bacteriophage T7 / Q000201:enzymology; D053487:DEAD-box RNA Helicases; D012321:DNA-Directed RNA Polymerases / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D007763:Lac Operon; D008969:Molecular Sequence Data; D017354:Point Mutation; D014176:Protein Biosynthesis / Q000502:physiology; D020365:RNA Helicases; D012316:RNA Nucleotidyltransferases / Q000502:physiology; D012329:RNA, Bacterial / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D013914:Threonine-tRNA Ligase / Q000235:genetics; D014158:Transcription, Genetic / Q000502:physiology; D014764:Viral Proteins
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D014764:Viral Proteins; D012316:RNA Nucleotidyltransferases; C062210:bacteriophage T7 RNA polymerase; D012321:DNA-Directed RNA Polymerases; C088840:deaD protein, E coli; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases; D013914:Threonine-tRNA Ligase