PPIase that acts as a histone chaperone (PubMed:14981505, PubMed:16846601). Histone proline isomerase that increases the rate of cis-trans isomerization at 'Pro-17' (H3P16), 'Pro-31' (H3P30) and 'Pro-39 (H3P38) on the histone H3 N-terminal tail (PubMed:16959570, PubMed:23888048). H3P16 and H3P30 are the major proline targets with little activity shown against H3P38 (PubMed:23888048). H3P38 isomerization influences SET2-mediated H3K36 methylation thereby regulating gene expression (PubMed:16959570). [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) Binds to histones H3 and H4 (PubMed:16959570). Interacts with NOP53. Present with 14100 molecules/cell in log phase SD medium. Belongs to the FKBP-type PPIase family. FKBP3/4 subfamily.