Loss of the bloom syndrome helicase increases DNA ligase 4-independent genome rearrangements and tumorigenesis in aging Drosophila
- Equal contributors
1 Department of Biology, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA
2 Department of Pathology, Tufts Medical Center, 800 Washington Street, Boston, MA 02111, USA
3 Department of Biology, Tufts University, 165 Packard Avenue, Medford, MA 02155, USA
4 Department of Genetics, Albert Einstein College of Medicine, 1301 Morris Park Avenue, Bronx, NY 10461, USA
Genome Biology 2011, 12:R121 doi:10.1186/gb-2011-12-12-r121Published: 19 December 2011
The BLM DNA helicase plays a vital role in maintaining genome stability. Mutations in BLM cause Bloom syndrome, a rare disorder associated with cancer predisposition and premature aging. Humans and mice with blm mutations have increased frequencies of spontaneous mutagenesis, but the molecular basis of this increase is not well understood. In addition, the effect of aging on spontaneous mutagenesis in blm mutants has not been characterized. To address this, we used a lacZ reporter system in wild-type and several mutant strains of Drosophila melanogaster to analyze mechanisms of mutagenesis throughout their lifespan.
Our data show that Drosophila lacking BLM have an elevated frequency of spontaneous genome rearrangements that increases with age. Although in normal flies most genome rearrangements occur through DNA ligase 4-dependent classical end joining, most rearrangements that accumulate during aging in blm mutants do not require DNA ligase 4, suggesting the influence of an alternative end-joining mechanism. Adult blm mutants also display reduced lifespan and ligase 4-independent enhanced tumorigenesis in mitotically active tissues.
These results suggest that Drosophila BLM suppresses error-prone alternative end-joining repair of DNA double-strand breaks that can result in genome instability and tumor formation during aging. In addition, since loss of BLM significantly affects lifespan and tumorigenesis, the data provide a link between error-prone end joining, genome rearrangements, and tumor formation in a model metazoan.