Structural basis of Q-dependent antitermination

Zhou Yin, Jason T. Kaelber, Richard H. Ebright

Research output: Contribution to journalArticle

3 Scopus citations


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, terminationdeficient 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 RNAexit channel, extruding topologically linked single-stranded RNA and preventing the formation of pause and terminator hairpins.

Original languageEnglish (US)
Pages (from-to)18384-18390
Number of pages7
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number37
StatePublished - Sep 10 2019

All Science Journal Classification (ASJC) codes

  • General


  • RNA polymerase
  • Transcription antitermination
  • Transcription antitermination factor Q
  • Transcription antitermination factor Q21
  • Transcription elongation complex

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