Gene Q antiterminator proteins of Escherichia coli phages 82 and lambda suppress pausing by RNA polymerase at a rho-dependent terminator and at other sites.

The Q genes of phages lambda and 82 encode transcription antiterminators that are active in vitro in a purified transcription system. Transcription termination is thought to involve two distinct steps: pausing of the transcription complex at the terminator and release of enzyme and RNA; either or both steps might be inhibited by Q protein. We show that Q-modified RNA polymerase pauses much less efficiently than does unmodified enzyme at the natural pause sites of a rho-dependent terminator as well as at other pause sites. This changed behavior can account for the termination properties of Q-modified RNA polymerase and reflects a fundamental alteration of the elongation properties of the enzyme.