期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 112, 期 44, 页码 13467-13472出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1515231112
关键词
single-molecule FRET; protein-DNA interaction dynamics; MerR-family regulators; metal-responsive transcription regulation
资金
- NIH [GM109993, GM106420, AI117295]
- Army Research Office Grant [W911NF1510268]
- NIH Chemistry and Biology Interface Trainee Grant [5T32GM008500]
- U.S. Department of Defense (DOD) [W911NF1510268] Funding Source: U.S. Department of Defense (DOD)
Metalloregulators respond to metal ions to regulate transcription of metal homeostasis genes. MerR-family metalloregulators act on sigma(70)-dependent suboptimal promoters and operate via a unique DNA distortion mechanism in which both the apo and holo forms of the regulators bind tightly to their operator sequence, distorting DNA structure and leading to transcription repression or activation, respectively. It remains unclear how these metalloregulator-DNA interactions are coupled dynamically to RNA polymerase (RNAP) interactions with DNA for transcription regulation. Using single-molecule FRET, we study how the copper efflux regulator (CueR)-a Cu+-responsive MerR-family metalloregulator-modulates RNAP interactions with CueR's cognate suboptimal promoter PcopA, and how RNAP affects CueR-PcopA interactions. We find that RNAP can form two noninterconverting complexes at PcopA in the absence of nucleotides: a dead-end complex and an open complex, constituting a branched interaction pathway that is distinct from the linear pathway prevalent for transcription initiation at optimal promoters. Capitalizing on this branched pathway, CueR operates via a biased sampling instead of dynamic equilibrium shifting mechanism in regulating transcription initiation; it modulates RNAP's binding-unbinding kinetics, without allowing interconversions between the deadend and open complexes. Instead, the apo-repressor form reinforces the dominance of the dead-end complex to repress transcription, and the holo-activator form shifts the interactions toward the open complex to activate transcription. RNAP, in turn, locks CueR binding at PcopA into its specific binding mode, likely helping amplify the differences between apo- and holo-CueR in imposing DNA structural changes. Therefore, RNAP and CueR work synergistically in regulating transcription.
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