BRCA1 mutation linked to genomic instability

The BRCA1 protein is a tumour suppressor associated with hereditary breast and ovarian cancer. Inder Verma and colleagues now describe a previously unknown function for BRCA1 that could be relevant to cancer causation. BRCA1 deficiency in mice is shown to impair the integrity of constitutive heterochromatin and to disrupt gene silencing at satellite repeat regions through the loss of ubiquitylation of histone H2A. Abnormal transcription of satellite repeats also occurs in human breast cancer samples deficient in BRCA1, a possible cause of genomic instability and thereby tumorigenesis.