THE OMPA 5' UNTRANSLATED REGION IMPEDES A MAJOR PATHWAY FOR MESSENGER-RNA DEGRADATION IN ESCHERICHIA-COLI

The unusual longevity of the Escherichia coil ompA transcript is deter mined by its 5' untranslated region (UTR), which functions in vivo as an mRNA stabilizer. Here we show that this 5' UTR can prolong the life time in E. coil of a variety of heterologous mRNAs to which it is join ed, either as a gene fusion or as an operon fusion. Statistical extrap olation suggests that it is quite likely that most E. coil mRNAs could be stabilized in this manner. We conclude that the ompA 5' UTR impede s a major pathway for mRNA degradation in E. coil and that stabilizati on by fusion to this UTR does not require translational readthrough of the heterologous mRNA segment by ribosomes that initiate translation at the ompA ribosome-binding site. Additional experiments indicate tha t the E. coil ribonuclease whose action is slowed by the ompA 5' UTR i s not RNase III.