DNAJC9 Integrates Heat Shock Molecular Chaperones into the Histone Chaperone Network

From biosynthesis to assembly into nucleosomes, histones are handed through a cascade of histone chaperones, which shield histones from non-specific interactions. Whether mechanisms exist to safeguard the histone fold during histone chaperone handover events or to release trapped intermediates is unclear. Using structure-guided and functional proteomics, we identify and characterize a histone chaperone function of DNAJC9, a heat shock co-chaperone that promotes HSP70-mediated catalysis. We elucidate the structure of DNAJC9, in a histone H3-H4 co-chaperone complex with MCM2, revealing how this dual histone and heat shock co-chaperone binds histone substrates. We show that DNAJC9 recruits HSP70-type enzymes via its J domain to fold histone H3-H4 substrates: upstream in the histone supply chain, during replication- and transcription-coupled nucleosome assembly, and to clean up spurious interactions. With its dual functionality, DNAJC9 integrates ATP-resourced protein folding into the histone supply pathway to resolve aberrant intermediates throughout the dynamic lives of histones. Overall design: Quantitative ChIP-seq analysis of DNAJC9 distribution and abundance from cells expressing DNAJC9-MYC-Flag WT, J or 4A mutants, and control cells . All experiments were done in duplicates. Chromatin of Drosophila melanogater S2 cells were used as spike-in for normalization purpose. Please note that each processed data was generated from both replicates (R1 and R2) and is linked to the corresponding R1 sample records.