Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 116, Issue 37, Pages 18384-18390Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1909801116
Keywords
transcription antitermination; transcription antitermination factor Q; transcription antitermination factor Q21; transcription elongation complex; RNA polymerase
Categories
Funding
- National Institutes of Health [GM041376]
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Lambdoid bacteriophage Q protein mediates the switch from middle to late bacteriophage gene expression by enabling RNA polymerase (RNAP) to read through transcription terminators preceding bacteriophage late genes. Q loads onto RNAP engaged in promoter-proximal pausing at a Q binding element (QBE) and adjacent sigma-dependent pause element (SDPE) to yield a Q-loading complex, and Q subsequently translocates with RNAP as a pausing-deficient, termination-deficient Q-loaded complex. Here, we report high-resolution structures of 4 states on the pathway of antitermination by Q from bacteriophage 21 (Q21): Q21, the Q21-QBE complex, the Q21-loading complex, and the Q21-loaded complex. The results show that Q21 forms a torus, a nozzle, that narrows and extends the RNAP RNA-exit channel, extruding topologically linked single-stranded RNA and preventing the formation of pause and terminator hairpins.
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