Dnj4HA AP-MS in Cryptococcus neoformans

Proteins which act as histone chaperones ensure genomic integrity during routine processes such as DNA replication and transcription as well as DNA repair upon damage. Herein, we identify a nuclear J domain protein, Dnj4, which interacts with histones 3 and 4 as well as Hsp71 as demonstrated in an AP-MS experiment suggesting that it integrates the heat shock chaperone machinery into histone chaperoning. In support of this, a deletion mutant lacking DNJ4 had higher levels of DNA damage than the wild type or complemented strains and was hypersensitive to DNA damaging agents. The transcriptional response to DNA damage in a mutant lacking DNJ4 was impaired. Genes related to DNA damage and iron homeostasis functions were up-regulated in the wild type strain in response to hydroxyurea treatment, however their up-regulation was either absent or reduced in a dnj4∆ mutant. Accordingly, excess iron rescued the mutant’s growth in response to hydroxyurea treatment. Iron homeostasis is crucial for virulence in Cryptococcus neoformans, however Dnj4 was found to be dispensable for virulence in a mouse model of cryptococcosis. Finally, we confirmed a conserved role of Dnj4 in histone chaperoning by expressing it in S. cerevisiae and showing that it disrupted endogenous histone chaperoning. Altogether, this study highlights the importance of a JDP co-chaperone in histone chaperoning in C. neoformans.