Background
p15 (PAF), also known as PAF, L5, OEATC1 (overexpressed in anaplastic thyroid carcinoma 1) or NS5ATP9, is a 111 amino acid protein that localizes to both the nucleus and the mitochondria. Highly expressed in colon and thymus with lower expression in liver, ovary, kidney, spleen, placenta and small intestine, p15 (PAF) interacts with the nuclear antigen PCNA and, through this interaction, is thought to protect cells from UV-induced cell death. The association of p15 (PAF) and PCNA is enhanced by UV treatment and is facilitated by the binding of ING1, a tumor suppressor that can induce apoptosis.