Messenger RNA processing in bacteria and eukaryotes. Eukaryotic mRNA undergoes several more steps than bacterial mRNA before translation. (a) Because bacterial cells lack a nucleus, transcription and translation are coupled. (b) In eukaryotic cells, transcription and pre-mRNA (precursor mRNA) processing occur in the nucleus, followed by export to the cytoplasm and subsequent translation. In both types of cells, the mRNA is eventually degraded.