Processing endoribonucleases and mRNA degradation in bacteria.

Forty years have passed since the dramatic identification of mRNA, the unstable carrier of genetic information from DNA to protein (15, 48, 56). During the last decade, there have been scores of papers and reviews that assume that RNase E is the central enzyme for degradation of mRNA. (There have been hundreds of papers and many reviews on RNase E and mRNA degradation, with at least 60 just in the last 2 years. I regret the unintentional omission of worthy ones but only refer to examples in this short presentation.) It is appropriate to consider evidence for and against this conclusion since it bears on our understanding of overall pathways of metabolism. RNase E was identified in 1978 by Apirion et al. (4, 44, 96) as an endoribonuclease (endo-RNase) that catalyzed the maturation of 5S rRNA by two sequential cleavages at specific sites of the 9S RNA of Escherichia coli. About the same time, Kuwano (recently from training with Apirion) et al. isolated an unusual temperature-sensitive mutant called the ams (for altered mRNA stability) mutant (73, 107). About a decade later, it was shown that the ams mutation maps in the gene for RNase E, rne (9, 95, 99, 130). This identification contributed to the now widely held view that RNase E is the principal RNase for initiation of mRNA decay (e.g., see references 33, 34, 35, 49, 57, 87, 122, and 124).