Drosophila FANCM helicase prevents spontaneous mitotic crossovers generated by the MUS81 and SLX1 nucleases.
Several helicases function during repair of double-strand breaks and handling of blocked or stalled replication forks to promote pathways that prevent formation of crossovers. Among these are the Bloom syndrome helicase BLM and the Fanconi anemia group M (FANCM) helicase. To better understand functions of these helicases, we compared phenotypes of Drosophila melanogaster Blm and Fancm mutants. As previously reported for BLM, FANCM has roles in responding to several types of DNA damage in preventing mitotic and meiotic crossovers and in promoting the synthesis-dependent strand annealing pathway for repair of a double-strand gap. In most assays, the phenotype of Fancm mutants is less severe than that of Blm mutants, and the phenotype of Blm Fancm double mutants is more severe than either single mutant, indicating both overlapping and unique functions. It is thought that mitotic crossovers arise when structure-selective nucleases cleave DNA intermediates that would normally be unwound or disassembled by these helicases. When BLM is absent, three nucleases believed to function as Holliday junction resolvases--MUS81-MMS4, MUS312-SLX1, and GEN--become essential. In contrast, no single resolvase is essential in mutants lacking FANCM, although simultaneous loss of GEN and either of the others is lethal in Fancm mutants. Since Fancm mutants can tolerate loss of a single resolvase, we were able to show that spontaneous mitotic crossovers that occur when FANCM is missing are dependent on MUS312 and either MUS81 or SLX1.
['Kuo|H Kenny|HK|', 'McMahan|Susan|S|', 'Rota|Christopher M|CM|', 'Kohl|Kathryn P|KP|', 'Sekelsky|Jeff|J|']
D000818:Animals D003434:Crossing Over, Genetic D004249:DNA Damage D004265:DNA Helicases D004268:DNA-Binding Proteins D029721:Drosophila Proteins D004331:Drosophila melanogaster D004706:Endodeoxyribonucleases D004720:Endonucleases D049750:Genome, Insect D008540:Meiosis D008938:Mitosis D009154:Mutation D010641:Phenotype D045522:Recombinases
helicase Fanconi anemia Holliday junction resolvase mitotic recombination