A new UC Davis study that explains the actions of a gene mutation that causes early onset cancer provides a fundamental insight into the mechanism of DNA-break repair.

Ionizing radiation, toxic chemicals, and other agents continually damage the body's DNA, threatening life and health: unrepaired DNA can lead to mutations, which in turn can lead to diseases like cancer. Intricate DNA repair mechanisms in the cells' nuclei are constantly working to fix what's broken, but whether the repair work happens "on the road" — right where the damage occurs — or "in the shop" — at specific regions of the nucleus — is an unanswered question.

Scientists from the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), National Cancer Institute (NCI), and Integrative Bioinformatics Inc. have made an important discovery about the role of an enzyme called ataxia telangiectasia mutated protein (ATM) in the body’s ability to repair damaged DNA. NIAMS and NCI are part of the National Institutes of Health (NIH).

Cells have the remarkable ability to keep track of their genetic contents and - when things go wrong - to step in and repair the damage before cancer or another life-threatening condition develops.

Investigators at St. Jude Children's Research Hospital had a molecule's eye view of the human cell's DNA repair kit as it assembled on a double-strand break to link together the broken ends. Double-strand breaks are ruptures that cut completely across the twisted, ladder-like structure of DNA, breaking it into two pieces.