Serine/threonine protein kinase which activates checkpoint signaling in the presence of DNA double strand breaks (DSBs) and other forms of DNA damage induced by ionizing radiation and other genotoxic stresses such as UV. Plays a role in maintaining genome stability. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Increased sensitivity to ionizing radiation with reduced survival compared to wild-type animals. Loss of induction of apoptosis following UV-C or ionizing radiation treatment but no effect on apoptotic response induced by X-ray exposure. Low brood size, reduced viability and sterility, appearance of a high-incidence-of-males (Him) phenotype, and reduced chromosome number due to chromosome fusions. Belongs to the PI3/PI4-kinase family. ATM subfamily.