DnaJ homolog subfamily C member 9

DNAJC9 (DnaJ homolog subfamily C member 9) is a 260-amino acid co-chaperone protein that functions as both a histone chaperone and heat shock protein 70 (HSP70) co-chaperone (UniProt: Q8WXX5). As a histone chaperone, it works with MCM2 to facilitate histone H3-H4 heterodimer recognition and nucleosome assembly, and may recruit additional histone chaperones such as ASF1A, NASP, and SPT2. It also serves as a co-chaperone for HSP70-family proteins including HSPA1A, HSPA1B, and HSPA8, helping maintain histone structural integrity and coordinate molecular chaperone machinery recruitment.

DNAJC9 is broadly expressed and participates in histone homeostasis and protein quality control pathways essential for chromatin regulation and cellular stress responses (UniProt: Q8WXX5). No specific genetic disease associations are currently listed in UniProt for this protein.

In Alzheimer's disease, DNAJC9 is upregulated in post-mortem brain tissue from AD patients compared to age-matched controls, with a mean log2 fold-change of 0.57 across one subcellular fraction in TMT-labeled proteomics analysis (Chaparral AD proteomics). This upregulation suggests a potential compensatory response to proteostatic stress or altered chromatin dynamics in the AD brain.