Abstract
Bacterial mRNAs begin with a triphosphate on the first transcribed nucleotide, but the endonuclease long thought to initiate mRNA decay in E. coli (RNase E) only works well on RNA with a 5′ monophosphate. The first committed step in the degradation of mRNA in that organism now appears to be the conversion of the 5′ triphosphate to a monophosphate, a process that is functionally similar to mRNA decapping in eukaryotes.