Parafibromin is a predominantly nuclear protein with a tumour suppressor role in the development of hereditary and nonhereditary parathyroid carcinomas, and the hyperparathyroidism-jaw tumour syndrome, which is associated with renal and uterine tumours. Parafibromin is a component of the highly conserved PAF1 complex, which regulates transcriptional events and histone modifications. The parafibromin/PAF1 complex regulates genes involved in cell growth and survival, and via these, parafibromin plays a pivotal role in embryonic development and survival of adults.