Cell division cycle 73, Paf1/RNA polymerase II complex component, homolog (S. cerevisiae), also known as CDC73 and parafibromin, is a protein which in humans is encoded by the CDC73 gene. Parafibromin, LEO1, PAF1, and CTR9 form the PAF protein complex, which associates with the RNA polymerase II subunit POLR2A and with a histone methyltransferase complex. Mutations in the CDC73 gene are associated with hyperparathyroidism-jaw tumor syndrome (HPT-JT) and parathyroid carcinomas.