PPIase that acts as a histone chaperone. Histone proline isomerase that increases the rate of cis-trans isomerization at prolines on the histone H3 N-terminal tail. Proline isomerization influences H3 methylation thereby regulating gene expression. [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) Inhibited by both FK506 and rapamycin. Binds to histones H3 and H4. Belongs to the FKBP-type PPIase family. FKBP3/4 subfamily. The predicted gene AN3908 has been split into 2 genes: AN10489 and AN10485.