The c-terminal domain of the alpha subunit of Escherichia coli RNA polymerase is required for efficient rho-dependent transcription termination

Abstract

We screened a collection of single alanine residue substitution mutants spanning the entire C-terminal domain of the alpha subunit (αCTD) of Escherichia coli RNA polymerase (RNAP) for defects in rho-dependent transcription termination at λtR1 in vivo and in vitro, and thereby identified a patch of amino acid residues in the αCTD required for efficient rho-dependent termination. NusA addition led to the stimulation of rho-dependent termination under our conditions in vitro. The termination defects of a few mutant RNAPs could be attributed to altered interactions with the NusA protein, but rho-dependent termination by most of the defective RNAPs was still stimulated normally by NusA. The NusA-enhanced transcription pausing behaviors of the mutant RNAPs did not always correlate with their rho-dependent termination phenotypes. We conclude that the αCTD is a target for interactions with NusA that influence both termination and pausing, but in addition it participates in rho-dependent transcription termination in a NusA-independent manner.