クロマチン構造による遺伝子の読み取り制御のメカニズムを解明――特殊なヌクレオソーム・オーバーラッピングダイヌクレオソームによる転写制御――

2026-06-25 東京大学,理化学研究所

クロマチン構造による遺伝子の読み取り制御のメカニズムを解明の概要

＜関連情報＞

• https://www.iqb.u-tokyo.ac.jp/pressrelease/260625/
• https://www.nature.com/articles/s41594-026-01837-0

六量体と八量体から形成される複合ヌクレオソームを介した非対称転写の構造的基盤 Structural basis of asymmetric transcription through a composite nucleosome formed by a hexasome and an octasome

Zhihui Chen  (陈之慧),Cheng-Han Ho  (何承翰),Hiroki Tanaka  (田中大貴),Tomoya Kujirai  (鯨井智也),Mitsuo Ogasawara  (小笠原光雄),Haruhiko Ehara  (江原晴彦),Shun-ichi Sekine  (関根俊一),Yoshimasa Takizawa  (滝沢由政) & Hitoshi Kurumizaka  (胡桃坂仁志)
Nature Structural & Molecular Biology  Published:25 June 2026
DOI:https://doi.org/10.1038/s41594-026-01837-0

Abstract

The overlapping dinucleosome (OLDN), a composite chromatin particle consisting of a hexasome and a canonical octasome, forms immediately downstream of transcription start sites, probably through chromatin remodeling activity, and has been proposed to act as a transient regulatory intermediate during transcription. Nevertheless, how RNA polymerase II (RNAPII) engages with and transcribes through this unusual structure has remained unclear. Here we reconstituted OLDNs in vitro and performed transcription assays with RNAPII. We found that transcription efficiency was markedly higher when RNAPII initiated from the hexasome side than from the octasome side. Cryo-electron microscopy further revealed that transcription from the hexasome side induced pronounced conformational rearrangements, in which RNAPII progression dramatically opened the hexasome–octasome interface. These results identify a mechanism by which RNAPII senses the intrinsic transcriptional polarity of OLDNs and suggest that OLDNs function as dynamic, directionally sensitive regulators of transcription elongation.