October 2005

Anti-checkpoint activity

A novel biological response to DSBs

Published in the latest G&D issue, Dr. Ted Weinert and colleagues (University of Arizona) describe a phenomena by which yeast telomeres may prevent the recognition of chromosome ends as double strand breaks (DSBs), subsequent cell cycle arrest, and ultimately, the end-to-end fusion of chromosomes.

The authors identified a stretch of internal telomeric repeats that attenuate the DNA damage checkpoint response elicited by nearby DSBs. DSBs adjacent to such telomeric sequences did initiate an arrest, but the duration was approximately 80% less than expected (1-2 hours versus 8-12 hours for a normal arrest response).

Further work is needed to delineate the mechanism of this telomere repeat-associated checkpoint suppression, but the authors are confident that "an anticheckpoint activity may be associated with normal telomeres to prevent them from being recognized as DSBs to cause cell cycle arrest."