POLYNUCLEOTIDE PHOSPHORYLASE IS REQUIRED FOR THE RAPID DEGRADATION OFTHE RNASE E-PROCESSED RPSO MESSENGER-RNA OF ESCHERICHIA-COLI DEVOID OF ITS 3'-HAIRPIN

The monocistronic transcript of rpsO undergoes an endonucleolytic clea vage downstream of the coding sequence, which removes the hairpin of t he transcription terminator and initiates the rapid degradation of the message. We demonstrate here that the two rne-dependent cleavages, on both sides of the transcription terminator, are catalysed by RNase E in vitro and that the RNase E-processed rpsO message is rapidly degrad ed by polynucleotide phosphorylase, while RNase II produces stable dec ay intermediates. Moreover, we show that RNase E cuts in vitro the cod ing sequence of the rpsO mRNA at several sites which are not detected in vivo.