RESTORATION OF TERMINATION BY RNA-POLYMERASE MUTATIONS IS RHO ALLELE-SPECIFIC

Mutations have been isolated which restore transcription termination at the termination signal at the end of the trp operon, ttrp, in a strain with a defective rho protein. The class of such mutations analyzed here is located in or close to the rpoBC operon, which encodes the β and β′ subunits of RNA polymerase. In a strain with one particular rho mutation, all mutant RNA polymerases restore termination at ttrp to the same degree, while in a strain carrying a different rho mutation, one mutant RNA polymerase restores termination to a much greater degree than do the other mutant polymerases. This rho allele specificity of the RNA polymerase mutations suggests that there may be a physical interaction between rho and RNA polymerase at rho-dependent termination sites of Escherichia coli. Alternative explanations for these results are discussed. © 1979.