A HUMAN RNASE E-LIKE ACTIVITY THAT CLEAVES RNA SEQUENCES INVOLVED IN MESSENGER-RNA STABILITY CONTROL

We have detected an endoribonucleolytic activity in human cell extract s that processes the Escherichia coli 9S RNA and outer membrane protei n A (ompA) mRNA with the same specificity as RNase E from E. coli. The human enzyme was partially purified by ion-exchange chromatography, a nd the active fractions contained a protein that was detected with ant ibodies shown to recognize E. coli RNase E. RNA containing four repeat s of the destabilizing motif AUUUA and RNA from the 3' untranslated re gion of human c-myc mRNA were also found to be cleaved by E. coli RNas e E and its human counterpart in a fashion that may suggest a role of this activity in mammalian mRNA decay. It was also found that RNA cont aining more than one AUUUA motif was cleaved more efficiently than RNA with only one or a mutated motif. This finding of a eukaryotic endori bonucleolytic activity corresponding to RNase E indicates an evolution ary conservation of the components of mRNA degradation systems.