Abstract 1732: Linker histone h1 inhibits topoisomerase IIa in vitro and in vivo

Abstract H1 linker histones play a crucial role in organizing chromatin into higher-order structures and regulating gene expression, contributing significantly to various cellular processes. Topoisomerase IIa (TopoIIa) is essential for multiple cellular functions via regulating DNA topology. Here, we report a direct interaction between H1 linker histones and TopoIIa through both N- and C-terminal domains of H1 variants. H1 suppresses the decatenation enzymatic activity of TopoIIa in vitro in a dose-dependent manner. Overexpressing specific H1 variants in HeLa cells results in a marked decrease in cell proliferation and a dramatic increase in the occurrence of cells displaying abnormal mitotic chromosomes. Additionally, we find that the inhibitory effect of the specific H1 variant on TopoIIa activity occurs prior to the formation of DNA-TopoIIa complexes. These results reveal a novel mechanistic link between histone H1 and Topo IIa in the regulation of chromatin function. Citation Format: Samantha Lasater, Hiba Hamdan, Po-Yi Ho, Ting Wu, Kaixiang Cao, Ruiqiao Yang, Yunzhe Zhang, Yuhong Fan. Linker histone h1 inhibits topoisomerase IIa in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1732.