Processing enzyme ribonuclease E specifically cleaves RNA I. An inhibitor of primer formation in plasmid DNA synthesis.

When the RNA processing enzyme RNAase E is inactivated in an Escherichia coli strain carrying derivatives of the colicin E1 plasmid, a small RNA, about 100 nucleotides long, accumulates. Structural analysis of this RNA showed that it is RNA I, the RNA that inhibits plasmid DNA synthesis. RNA I is a specific substrate for RNAase E and the cleavage takes place between the fifth and sixth nucleotides from the 5' end of the molecule. This is only the second natural RNA substrate that has been found, so far, for the RNA processing enzyme ribonuclease E, the other being a precursor for 5 S ribosomal RNA. It is remarkable that nine nucleotides around the cleavage sites are identical in both substrates: (Formula: see text). Therefore, we suggest that at least part of the interaction between RNAase E and its substrate is controlled by these nine nucleotides.