A study published in the October issue of Nature Genetics demonstrates that loss of the tumor-suppressor protein p53, coupled with elimination of the DNA-maintenance protein ATR, severely disrupts tissue maintenance in mice. As a result, tissues deteriorate rapidly, which is generally fatal in these animals. In addition, the study provides supportive evidence for the use of inhibitors of ATR in cancer therapy.Essentially, says senior author Eric Brown, PhD, Assistant Professor of Cancer Biology at the University of Pennsylvania School of Medicine, the findings highlight the fact that day-to-day maintenance required to keep proliferative tissues like skin and intestines functional is about more than just regeneration, a stem cell-based process that forms the basis of tissue renewal. It's also about housekeeping, the clearing away of damaged cells. Whereas loss of ATR causes DNA damage, the job of p53 is to monitor cells for such damage and either stimulate the early demise of such cells or prevent their replication, the housekeeping part of the equation. The findings indicate that as messy as things can become in the absence of a DNA maintenance protein like ATR, failing to remove resulting damaged cells by also deleting p53, is worse. "Because the persistence of damaged cells in the absence of p53 prevents appropriate tissue renewal, these and other studies have underscored the importance not only of maintaining competent stem cells, but also of eliminating what gets in the way of regeneration," explains Brown.
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