Mechanisms of DNA opening revealed in AAA+ transcription complex structures
Science Advances(2022)
摘要
Gene transcription is carried out by RNA polymerase (RNAP) and requires the conversion of the initial closed promoter complex, where DNA is double stranded, to a transcription-competent open promoter complex, where DNA is opened up. In bacteria, RNAP relies on σ factors for its promoter specificities. Using a special form of sigma factor (σ 54 ), which forms a stable closed complex and requires its activator that belongs to the AAA+ ATPases (ATPases associated with diverse cellular activities), we obtained cryo–electron microscopy structures of transcription initiation complexes that reveal a previously unidentified process of DNA melting opening. The σ 54 amino terminus threads through the locally opened up DNA and then becomes enclosed by the AAA+ hexameric ring in the activator-bound intermediate complex. Our structures suggest how ATP hydrolysis by the AAA+ activator could remove the σ 54 inhibition while helping to open up DNA, using σ 54 amino-terminal peptide as a pry bar.
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关键词
dna opening
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