Chromatin Buffers Torsional Stress During Transcription.

TitleChromatin Buffers Torsional Stress During Transcription.
Publication TypeJournal Article
Year of Publication2024
AuthorsQian J, Lubkowska L, Zhang S, Tan C, Hong Y, Fulbright RM, Inman JT, Kay TM, Jeong J, Gotte D, Berger JM, Kashlev M, Wang MD
JournalbioRxiv
Date Published2024 Oct 18
ISSN2692-8205
Abstract

Transcription through chromatin under torsion represents a fundamental problem in biology. Pol II must overcome nucleosome obstacles and, because of the DNA helical structure, must also rotate relative to the DNA, generating torsional stress. However, there is a limited understanding of how Pol II transcribes through nucleosomes while supercoiling DNA. In this work, we developed methods to visualize Pol II rotation of DNA during transcription and determine how torsion slows down the transcription rate. We found that Pol II stalls at ± 9 pN·nm torque, nearly sufficient to melt DNA. The stalling is due to extensive backtracking, and the presence of TFIIS increases the stall torque to + 13 pN·nm, making Pol II a powerful rotary motor. This increased torsional capacity greatly enhances Pol II's ability to transcribe through a nucleosome. Intriguingly, when Pol II encounters a nucleosome, nucleosome passage becomes more efficient on a chromatin substrate than on a single-nucleosome substrate, demonstrating that chromatin efficiently buffers torsional stress via its torsional mechanical properties. Furthermore, topoisomerase II relaxation of torsional stress significantly enhances transcription, allowing Pol II to elongate through multiple nucleosomes. Our results demonstrate that chromatin greatly reduces torsional stress on transcription, revealing a novel role of chromatin beyond the more conventional view of it being just a roadblock to transcription.

DOI10.1101/2024.10.15.618270
Alternate JournalbioRxiv
PubMed ID39464147
PubMed Central IDPMC11507789
Grant ListR01 GM136894 / GM / NIGMS NIH HHS / United States
T32 GM008267 / GM / NIGMS NIH HHS / United States