DNA-repair proteins perform a vital function and protect against potentially catastrophic events such as cancer-causing mutations or chromosome rearrangements, which are hallmarks of tumor cells.

Howard Hughes Medical Institute investigator Nikola P. Pavletich and his colleagues at Memorial Sloan-Kettering Cancer Center used x-ray crystallography to obtain "molecular snapshots" of the BRCA2 protein. The images produced by Pavletich's team show that BRCA2 is capable of binding to DNA, a conclusion that is supported by the group's biochemical experiments. The research was published in the September 13, 2002, issue of the journal Science.

The scientists were investigating the role of BRCA2 in homologous recombination, which is one of the ways that cells repair broken chromosomes. In this type of DNA repair, broken chromosomes are fixed by using the information from a sister chromosome as a template and "splint" to guide repair. This type of DNA repair is accurate and is the optimal mode of repair in dividing cells. Prior to the studies by Pavletich and his colleagues, BRCA2 was believed to play only an indirect regulatory role in DNA repair.

"BRCA2 had been previously implicated in the control of homologous recombination, although its precise role in this process was unknown," said HHMI investigator Stephen J. Elledge, who is at Baylor College of Medicine. "The significance of the structural studies of BRCA2 by Pavletich's group is that they provide evidence for a direct and unexpected biochemical role for BRCA2 in the enzymology of homologous recombination itself. It was an
'"/>

Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
12-Sep-2002