DNA Repair Proteins Monitored At Double-Strand Break
DNA Repair Proteins
St. Jude researchers have tracked the movement of the cell's DNA repair kit proteins as they interact with each other and gather at the site of damage.
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.
The St. Jude researchers could determine when repair proteins arrived at or around the DNA break and evaluate its repair -- even when particular proteins shifted away from the break to make room for others. A report on this work appears in the May 7 online issue of "Nature Cell Biology."
The findings are important because disruption of the precise movement of these repair proteins can cause mutations, cell death or cancer, and the ability to track the process so closely will give researchers critical insights into what can go wrong with DNA repair. This could lead to novel ways to make cancer cells more sensitive to therapy by blocking their ability to repair double-stranded breaks caused by chemotherapy or radiation. It could also suggest new strategies for enhancing repair of double-stranded DNA caused by radiation, natural oxidants in food or the body, and other toxins that can cause disease and aging.
"Prior to this work, there was no practical and efficient way to find and study the DNA repair proteins that organize themselves on and around a double- strand break in human cells," said Michael Kastan, M.D., Ph.D., St. Jude Cancer Center director. "Our approach solved that problem and allowed us to document the cell's response to double-strand DNA breaks over time." Kastan is the paper's senior author.
The assay, developed by Elijahu Berkovich, Ph.D., in Kastan's laboratory, demonstrates how key repair proteins, such as ATM, NBS1, XRCC4 and gamma-H2AX, interact to coordinate repair of double-strand breaks.
The other author of this article was Raymond Monnat, M.D. (University of Washington).
This work was supported in part by the National Institutes of Health and ALSAC.