AI Article Synopsis
- The CII protein from bacteriophage λ enhances transcription by binding to repeats near the promoter's -35 element.
- Recent studies have identified the structure of an intact λCII-dependent transcription activation complex (TAC-λCII) using cryo-electron microscopy, providing insights into how λCII interacts with RNA polymerase and the promoter.
- This study offers new perspectives on the mechanism of λCII-mediated transcription activation by comparing the structures of TAC-λCII and an RNAP-promoter open complex.
Article Abstract
The CII protein of bacteriophage λ activates transcription from the phage promoters P, P, and P by binding to two direct repeats that straddle the promoter -35 element. Although genetic, biochemical, and structural studies have elucidated many aspects of λCII-mediated transcription activation, no precise structure of the transcription machinery in the process is available. Here, we report a 3.1-Å cryo-electron microscopy (cryo-EM) structure of an intact λCII-dependent transcription activation complex (TAC-λCII), which comprises λCII, E. coli RNAP-σ holoenzyme, and the phage promoter P. The structure reveals the interactions between λCII and the direct repeats responsible for promoter specificity and the interactions between λCII and RNAP α subunit C-terminal domain responsible for transcription activation. We also determined a 3.4-Å cryo-EM structure of an RNAP-promoter open complex (RPo-P) from the same dataset. Structural comparison between TAC-λCII and RPo-P provides new insights into λCII-dependent transcription activation.
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| http://dx.doi.org/10.1016/j.str.2023.05.008 | DOI Listing |
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