Promotion of RNF168‐Mediated Nucleosomal H2A Ubiquitylation by Structurally Defined K63‐Polyubiquitylated Linker Histone H1

di-nucleosome substrate, revealing a comparable stimulation effect of both the inter- and intra-nucleosomal crosstalk. Overall, our study highlights the significance of access to structurally defined polyubiquitylated H1.0 by the CAEPL strategy, enabling in-depth mechanistic investigations of in-trans PTM crosstalk between linker histone H1.0 and core histone H2A ubiquitylation.