Crl Facilitates RNA Polymerase Holoenzyme Formation

Abstract
TheEscherichia coliCrl protein has been described as a transcriptional coactivator for the stationary-phase sigma factor σS. In a transcription system with highly purified components, we demonstrate that Crl affects transcription not only by the EσSRNA polymerase holoenzyme but also by Eσ70and Eσ32. Crl increased transcription dramatically but only when the σ concentration was low and when Crl was added to σ prior to assembly with the core enzyme. Our results suggest that Crl facilitates holoenzyme formation, the first positive regulator identified with this mechanism of action.

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