2026-07-06 理化学研究所
精製タンパク質を使った染色体再構成
＜関連情報＞
- https://www.riken.jp/press/2026/20260706_1/index.html
- https://academic.oup.com/pnasnexus/article/5/6/pgag218/8708689
生化学的再構成によって明らかになったコンデンシンIの二重リン酸化調節機構 Dual phosphoregulatory mechanisms of condensin I revealed by biochemical reconstitution
Keishi Shintomi,Shoji Tane,Yuki Masahara-Negishi,Tatsuya Hirano
PNAS Nexus Published:16 June 2026
DOI:https://doi.org/10.1093/pnasnexus/pgag218
Abstract
Exactly how cell cycle regulators control sequential large-scale transformations of chromatin structure during mitosis is not fully understood. Here, through biochemical reconstitution with a minimal set of recombinant proteins, we demonstrate that the assembly and disassembly of mitotic chromatids are orchestrated by dual modes of phosphoregulation of condensin I. First, cyclin B-Cdk1 phosphorylates the terminal intrinsically disordered regions (tIDRs) of the non-structural maintenance of chromosome subunits, releasing condensin I from self-suppression imposed by these regions. Second, phosphorylation of a conserved residue in the central region of the kleisin subunit CAP-H by Cdk1 is essential for the full activation of condensin I. Conversely, addition of the protein phosphatase PP2A-B55 is sufficient to trigger the dissociation of condensin I from reconstituted chromatids, thereby driving their disassembly. Complementary analyses using Xenopus egg extracts reveal that the tIDRs and the kleisin central region are phosphorylated and dephosphorylated with distinct kinetics during mitotic entry and exit. Together, these findings uncover an elaborate yet streamlined regulatory network that tightly couples chromatid assembly and disassembly to mitotic progression.
