PMID: 30795892

Authors:

Krupp F, Said N, Huang YH, Loll B, Burger J, Mielke T, Spahn CMT, Wahl MC

Title:

Structural Basis for the Action of an All-Purpose Transcription Anti-termination Factor.

Journal:

Mol Cell. 2019 Feb 12. pii: S1097-2765(19)30036-X. doi:, 10.1016/j.molcel.2019.01.016.

Abstract:

Bacteriophage lambdaN protein, a model anti-termination factor, binds nascent RNA and host Nus factors, rendering RNA polymerase resistant to all pause and termination signals. A 3.7-A-resolution cryo-electron microscopy structure and structure-informed functional analyses reveal a multi-pronged strategy by which the intrinsically unstructured lambdaN directly modifies RNA polymerase interactions with the nucleic acids and subverts essential functions of NusA, NusE, and NusG to reprogram the transcriptional apparatus. lambdaN repositions NusA and remodels the beta subunit flap tip, which likely precludes folding of pause or termination RNA hairpins in the exit tunnel and disrupts termination-supporting interactions of the alpha subunit C-terminal domains. lambdaN invades and traverses the RNA polymerase hybrid cavity, likely stabilizing the hybrid and impeding pause- or termination-related conformational changes of polymerase. lambdaN also lines upstream DNA, seemingly reinforcing anti-backtracking and anti-swiveling by NusG. Moreover, lambdaN-repositioned NusA and NusE sequester the NusG C-terminal domain, counteracting rho-dependent termination. Other anti-terminators likely utilize similar mechanisms to enable processive transcription.