Human Pin1 is a peptidyl-prolyl cis/trans isomerase (PPIase) that interacts with NIMA and essential for cell cycle regulation. Pin1 is nuclear PPIase containing a WW protein interaction domain, and is structurally and functionally related to Ess1/Ptf1, an essential protein in budding yeast. PPIase activity is necessary for Ess1/Pin1 function in yeast. Pin1 is thus an essential PPIase that regulates mitosis presumably by interacting with NIMA and attenuating its mitosis-promoting activity. Substrates of Pin1 include the mitotic regulators (Cdc25 phosphatase and NIMA ,PLK I, Wee, and Myt1 kinases), several transcription factors like beta-Catenin, c-Jun, and the tumor suppressor protein p53 , and some specific proteins like the RNA Pol II, the cytoskeleton protein tau, and the G1/S protein Cyclin D1. Alternative Names: Rotamase Pin1 protein, UBL5 protein, PPIase protein, Peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 protein, Pin -1 protein, Pin -1, Pin 1, PPIase Pin1 protein, Pin 1 protein, PPIase Pin1 protein, Rotamase Pin1 protein, DOD protein, Peptidyl-prolyl cis-trans isomerase NIMA-interacting 1, PIN1 protein, PIN1 protein, EC 5.2.1.8 protein, Pin 1, EC 5.2.1.8 protein