A protein long known to be involved in protecting cells from genetic damage has been found to play an even more important role in protecting the cell's offspring. New research by a team of scientists at Rockefeller University, Howard Hughes Medical Institute and the National Cancer Institute shows that the protein, known as ATM, is not only vital for helping repair double-stranded breaks in DNA of immune cells, but is also part of a system that prevents genetic damage from being passed on when the cells divide.

Early in the life of B lymphocytes -- the immune cells responsible for hunting down foreign invaders and labeling them for destruction -- they rearrange their DNA to create various surface receptors that can accurately identify different intruders, a process called V(D)J recombination. Now, in an study published online today in the journal Cell, Rockefeller University Professor Michel Nussenzweig, in collaboration with his brother Andr Nussenzweig at NCI and their colleagues, shows that when the ATM protein is absent, chromosomal breaks created during V(D)J recombination go unrepaired, and checkpoints that normally prevent the damaged cell from replicating are lost.

Normal lymphocytes contain a number of restorative proteins, whose job it is to identify chromosomal damage and repair it or, if the damage is irreparable, prevent the cell from multiplying. Earlier research by Andr and Michel Nussenzweig, who is an investigator at HHMI, had identified other DNA repair proteins that are important during different phases of a B lymphocyte's life. It was during one of these studies, which examined genetic damage late in the life of a B cell, that they came across chromosomal breaks that could not be explained.

So the researchers began to look into the potential role of V(D)J recombination. "We were not expecting it to be responsible for the breaks we were seeing," says Michel, Sherman Fairchild Professor and head of the Laboratory of
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Contact: Joseph Bonner
bonnerj@rockefeller.edu
212-327-8998
Rockefeller University
28-Jun-2007