BRCA1-deficient Cell (image) Rockefeller University Press Caption A JCB study determined how BRCA1-deficient cells protect themselves from genomic instability. The cells can accumulate fused and broken chromosomes (see image) because they can't use homologous recombination to repair their DNA. But the cells can resume proliferation by cranking up their output of cathepsin L, which destroys 53BP1, a protein that prods the cells to use alternative, sloppier repair mechanisms. Credit Susana Gonzalo Usage Restrictions Reporters may freely use these materials in news coverage, with the appropriate credit information. Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.