DNA-bend modulation in a repressor-to-activator switching mechanism.

摘要: RECENT discoveries of activator proteins that distort DNA but bear no obvious activation domains have focused attention on the role structure in transcriptional regulation1. Here we describe how transcription factor MerR can mediate repression as well through stereospecific modulation structure. The represser form binds between –10 and –35 promoter elements bacterial mercury-detoxification genes, PT, allowing RNA polymerase to an inactive complex with PT at this stress-inducible promoter2,3. Upon mercuric ion binding, Hg–MerR converts into transcriptionally active or 'open' form2–4. We show here bends towards itself a manner similar catabolite-activator protein CAP, namely two loci demarked by DNase I sensitivity, conformation, Hg–MerR, relaxes these bends. This activator-induced unbending, when coupled previously described untwisting operator5, remodels makes it better template for poised polymerase.