ATR Protein

ATR belongs to the PI3/PI4-kinase family, and is most closely related to ATM, a protein kinase which share similarity with Schizosaccharomyces pombe rad3, a cell cycle checkpoint gene required for cell cycle arrest and DNA damage repair in response to DNA damage. ATR is shown to phosphorylate checkpoint kinase CHK1, checkpoint proteins RAD17, and RAD9, as well as tumor suppressor protein BRCA1. ATR is an essential regulator of genomic integrity, controls and coordinates DNA-replication origin firing, replication-fork stability, cell cycle checkpoints, and DNA repair (1). ATR/ATM-dependent phosphorylation of RAD17 is a critical early event during checkpoint signaling in DNA-damaged cells (2).