The protein encoded by the tumor-suppressor gene BRCA1 may keep breast and ovarian cancer in check by preventing transcription of repetitive DNA sequences, according to a study published in Nature. This explanation brings together many disparate theories about how the gene functions and could also shed light on how other tumor suppressors work. Along with the usual problems attributed to defects in BRCA1 (in areas such as cell-cycle regulation and DNA repair), the authors also found in these cells a surprising paucity of 'heterochromatic centres' — dense packages of normally untranscribed, repetitive sequences of DNA near a chromosome's centromere. Instead, these DNA regions were highly active, churning out large numbers of RNA transcripts called satellite repeats. Because of this, the study may also have much broader significance, comments Roger Greenberg, PhD, associate professor of Cancer Biology, in Scientific American.
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