THE ROLE OF ENDONUCLEASES IN THE EXPRESSION OF RIBONUCLEASE-II IN ESCHERICHIA-COLI

Ribonuclease II (RNase II), encoded by the mb gene, is one of the two major Escherichia coli exonucleases involved in mRNA degradation. Some of the ribonucleases implicated in this process have recently been sh own to be inter-regulated. In this paper we studied the effects of the endonucleases RNase E and RNase III in mb expression. We have shown t hat RNase E cleaves the mb message internally: when this ribonuclease is inactivated rnb mRNA accumulates with a concomitant increase in RNa se II activity. RNase III also affects RNase II expression but in an i ndirect way. We discuss these implications for the regulation of mRNA degradation.