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| Title | In transcription antitermination by Qλ, NusA induces refolding of Qλ to form a nozzle that extends the RNA polymerase RNA-exit channel. |
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| Journal, issue, pages | Proc Natl Acad Sci U S A, Vol. 119, Issue 33, Page e2205278119, Year 2022 |
| Publish date | Aug 16, 2022 |
 Authors | Zhou Yin / Jeremy G Bird / Jason T Kaelber / Bryce E Nickels / Richard H Ebright /  |
| PubMed Abstract | Lambdoid bacteriophage Q proteins are transcription antipausing and antitermination factors that enable RNA polymerase (RNAP) to read through pause and termination sites. Q proteins load onto RNAP ...Lambdoid bacteriophage Q proteins are transcription antipausing and antitermination factors that enable RNA polymerase (RNAP) to read through pause and termination sites. Q proteins load onto RNAP engaged in promoter-proximal pausing at a Q binding element (QBE) and adjacent sigma-dependent pause element to yield a Q-loading complex, and they translocate with RNAP as a pausing-deficient, termination-deficient Q-loaded complex. In previous work, we showed that the Q protein of bacteriophage 21 (Q21) functions by forming a nozzle that narrows and extends the RNAP RNA-exit channel, preventing formation of pause and termination RNA hairpins. Here, we report atomic structures of four states on the pathway of antitermination by the Q protein of bacteriophage λ (Qλ), a Q protein that shows no sequence similarity to Q21 and that, unlike Q21, requires the transcription elongation factor NusA for efficient antipausing and antitermination. We report structures of Qλ, the Qλ-QBE complex, the NusA-free pre-engaged Qλ-loading complex, and the NusA-containing engaged Qλ-loading complex. The results show that Qλ, like Q21, forms a nozzle that narrows and extends the RNAP RNA-exit channel, preventing formation of RNA hairpins. However, the results show that Qλ has no three-dimensional structural similarity to Q21, employs a different mechanism of QBE recognition than Q21, and employs a more complex process for loading onto RNAP than Q21, involving recruitment of Qλ to form a pre-engaged loading complex, followed by NusA-facilitated refolding of Qλ to form an engaged loading complex. The results establish that Qλ and Q21 are not structural homologs and are solely functional analogs. |
 External links | Proc Natl Acad Sci U S A / PubMed:35951650 / PubMed Central |
| Methods | EM (single particle) / X-ray diffraction |
| Resolution | 1.46 - 3.36 Å |
| Structure data | EMDB-26438, PDB-7ubm: EMDB-26439, PDB-7ubn:  PDB-7ubj:  PDB-7ubk:  PDB-7ubl: |
| Chemicals |  ChemComp-ZN:  ChemComp-CL:  ChemComp-GOL:  ChemComp-EDO:  ChemComp-PEG:  ChemComp-PO4:  ChemComp-HOH:  ChemComp-MG: |
| Source |
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 Keywords | GENE REGULATION / RNA polymerase / DNA Binding / transcription / Q-dependent antitermination / Q antitermination factor / GENE REGULATION/DNA / GENE REGULATION-DNA complex / TRANSFERASE/DNA/RNA / TRANSFERASE-DNA-RNA complex |
escherichia coli (E. coli)
escherichia phage lambda (virus)