期刊
NATURE
卷 565, 期 7739, 页码 382-+出版社
NATURE PUBLISHING GROUP
DOI: 10.1038/s41586-018-0840-5
关键词
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资金
- NIH National Institute of General Medical Sciences [GM103310]
- NYSTAR
- Simons Foundation [349247]
- NIH [R35 GM118130, R01 GM114450]
A key regulated step of transcription is promoter melting by RNA polymerase (RNAP) to form the open promoter complex(1-3). To generate the open complex, the conserved catalytic core of the RNAP combines with initiation factors to locate promoter DNA, unwind 12-14 base pairs of the DNA duplex and load the template-strand DNA into the RNAP active site. Formation of the open complex is a multi-step process during which transient intermediates of unknown structure are formed(4-6). Here we present cryo-electron microscopy structures of bacterial RNAP-promoter DNA complexes, including structures of partially melted intermediates. The structures show that late steps of promoter melting occur within the RNAP cleft, delineate key roles for fork-loop 2 and switch 2-universal structural features of RNAP-in restricting access of DNA to the RNAP active site, and explain why clamp opening is required to allow entry of single-stranded template DNA into the active site. The key roles of fork-loop 2 and switch 2 suggest a common mechanism for late steps in promoter DNA opening to enable gene expression across all domains of life.
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