Construction and characterization of an absolute deletion mutant of Escherichia coli ribonuclease II.

The degradation of mRNA plays a central role in the control of protein synthesis. In Escherichia coli, the rnb gene encodes ribonuclease II (RNase II), one of the two main exonucleases involved in mRNA decay. We have constructed strain CMA201, in which the rnb promoter region and the gene were deleted from the chromosome and replaced by a tetr cassette. This is the first rnb absolute deletion mutant that shows the complete absence of rnb-specific mRNA. This strain has growth characteristics similar to the wild-type, even though it has no RNase II activity, and it should be useful in studies of mRNA metabolism.