United Press International

　　Monday, December 27, 2004

　　SAN DIEGO, Dec 27, 2004 (United Press International via COMTEX) —— Embryonic stem cells, proto-cells that become the different cells in a baby, have a safety mechanism to prevent passing on damaged DNA, U.S. scientists report.

　　Stem cells can multiply an unlimited number of times and become any cell in the body. These genetic engines, the hope of researchers looking to heal spinal injuries and cure diabetes, could also devastate an individual with cancer or other illness if a mutation were endlessly passed on.

　　Researchers working with mouse cells at the University of California, San Diego, found protein p53, which helps suppress tumors in humans and mice. This protein also helps maintain genetic stability by directly suppressing a gene for unlimited cell duplication in embryonic stem cells.

　　"What we discovered is a primary mechanism that allows embryonic stem cells to perform quality control inspections during their self-renewal, the process by which these cells undergo unlimited cellular division to produce an unlimited number of daughter cells," wrote Yang Xu, an associate professor of biology at UCSD.