mRNAs can be stabilized by DEAD-box proteins

Abstract

EUBACTERIAL messenger RNAs are synthesized and translated simultaneously; moreover the speed of ribosomes usually matches that of RNA polymerase^1,2. 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 β-galactosidase yield per transcript is depressed 100-fold. But the overexpression of DEAD-box proteins³ 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 unstable⁴ and we propose that DEAD-box proteins protect them from endonucleases. These results pinpoint the importance of transcription–translation syn-chronization for mRNA stability, and reveal an undocumented property of DEAD-box RNA helicases. These proteins have been implicated in a variety of processes involving RNA⁵ but not mRNA stability.