Growth defect and mutator phenotypes of RecQ-deficient Neurospora crassa mutants separately result from homologous recombination and nonhomologous end joining during repair of DNA double-strand breaks

RecQ helicases function in the maintenance of genome stability in many organisms. The filamentous fungus Neurospora crassa has two RecQ homologues, QDE3 and RECQ2. We found that the qde-3 recQ2 double mutant showed a severe growth defect. The growth defect was alleviated by mutation in mei-3, the homologue of yeast RAD51, which is required for homologous recombination (HR), suggesting that HR is responsible for this phenotype. We also found that the qde-3 recQ2 double mutant showed a mutator phenotype, yielding mostly deletions. This phenotype was completely suppressed by mutation of mus-52, the homologue of the human KU80 gene, required for nonhomologous end joining (NHEJ), but was unaffected by mutation in mei-3. The high spontaneous mutation frequency in the double mutant is thus likely to be due to NHEJ acting on an elevated frequency of double-strand breaks (DSBs) and we therefore suggest that QDE3 and RECQ2 maintain chromosome stability by suppressing the formation of spontaneous DSBs.

Key Words: Neurospora crassa, RecQ, genome instability, homologous recombination, nonhomologous end joining

This article has been cited by other articles:

				R. M. Brosh Jr and V. A. Bohr Human premature aging, DNA repair and RecQ helicases Nucleic Acids Res., December 3, 2007; 35(22): 7527 - 7544. [Abstract] [Full Text] [PDF]

Online ISSN: 1943-2361  Print ISSN: 0016-6731
Copyright 2009 by the Genetics Society of America
phone: 412-268-1812   fax: 412-268-1813   email: genetics-gsa{at}andrew.cmu.edu