Peptidyl-prolyl cis-trans isomerase NIMA-interacting 4(PIN4) is a peptidyl-prolyl cis/trans isomerase (PPIase) which interacts with NIMA and is vital for cell cycle regulation. PIN4 has 2 different isoforms: PAR14 and PAR17. Furthermore, PIN4 protein binds to double-stranded DNA under physiological salt conditions. PIN4 is involved as a ribosomal RNA processing factor in ribosome biogenesis. The PAR14 binds to tightly bent AT-rich stretches of double-stranded DNA, but PAR17 binds to double-stranded DNA.