COUPLING BETWEEN MESSENGER-RNA SYNTHESIS AND MESSENGER-RNA STABILITY IN ESCHERICHIA-COLI

Transiently stable products derived from the endonuclease cleavage of transcripts from the secEnusG and rplKAJLrpoSC operons have been ident ified. Cleavage sites for RNase III occur in the leader of the secEnus G transcript and in the L12-beta intercistronic space of the rplKAJLrp oSC transcript. A single RNase E cleavage site was located in the L1-L 10 intergenic space. Inactivation of RNase III and RNase E results res pectively in a one- to twofold and a greater than 10-fold stabilizatio n of five mRNA sequences from within the secE, nusG, L11-L1, L10 and b eta encoding cistrons. The relative amounts of each of these five mRNA sequences were found to be nearly constant when measured either in th e presence or absence of cleavage by RNase III or RNase E. This clearl y implies that any increases in the stability of these mRNA sequences resulting from the inactivation of processing by RNase III or RNase E are counterbalanced by changes in the mRNA synthesis rates. The mechan ism that links mRNA synthesis to mRNA decay is not known.