An essential role forDrosophila hus1in somatic and meiotic DNA damage responses

Abstract

The checkpoint proteins Rad9, Rad1 and Hus1 form a clamp-like complex which plays a central role in the DNA-damage-induced checkpoint response. Here we address the function of the 9-1-1 complex in Drosophila. We decided to focus our analysis on the meiotic and somatic requirements of hus1. For that purpose, we created a null allele of hus1 by imprecise excision of a P element found 2 kb from the 3′ of the hus1 gene. We found that hus1 mutant flies are viable, but the females are sterile. We determined that hus1 mutant flies are sensitive to hydroxyurea and methyl methanesulfonate but not to X-rays, suggesting that hus1 is required for the activation of an S-phase checkpoint. We also found that hus1 is not required for the G2-M checkpoint and for post-irradiation induction of apoptosis. We subsequently studied the role of hus1 in activation of the meiotic checkpoint and found that the hus1 mutation suppresses the dorsal-ventral pattering defects caused by mutants in DNA repair enzymes. Interestingly, we found that the hus1 mutant exhibits similar oocyte nuclear defects as those produced by mutations in DNA repair enzymes. These results demonstrate that hus1 is essential for the activation of the meiotic checkpoint and that hus1 is also required for the organization of the oocyte DNA, a function that might be independent of the meiotic checkpoint.

Clamping down on mammalian meiosis

“…Genetic analyses in lower eukaryotes, particularly in budding yeast, 13,53 worms, 11 and flies, 7,8 have established a role for 9-1-1 in promoting meiotic DSB repair. In yeast, rad17 (mammalian Rad1) and rad24 (a 9-1-1 clamp loader subunit) mutants exhibit delayed meiotic DSB repair that results in an altered ratio of crossover-to-noncrossover products.…”

“…In budding yeast 5,9,12 and other model organisms, 7,11,86,87 meiotic checkpoints have been well described and contain at least 2 major (yet intertwined) branchessynapsis monitoring and DSB repair monitoring-both of which primarily occur during the pachytene stage and thus have been termed branches of the pachytene checkpoint. It is not clear whether or how meiotic checkpoints operate in mammals, though it seems likely that there are multiple mechanisms that monitor and regulate progression through meiosis.…”

“…Studies in lower eukaryotes suggest that the 9-1-1 complex may have critical roles in meiotic recombination and homologous chromosome synapsis as well as meiotic checkpoint signaling. [4][5][6][7][8][9][10][11][12][13] The germline functions of mammalian 9-1-1 were investigated in 2 recent studies in which conditional mutations in Rad9a 14 and Hus1 15 were targeted to undifferentiated spermatogonia using mice that express CRE recombinase under the control of the Stra8 promoter.…”

“…53 In Drosophila hus1 mutant oocytes, DSBs are not processed efficiently, and oocyte nuclear defects are abrogated by blockage of DSB formation. 7,8 Drosophila oocytes also exhibit a genetic interaction between hus1 and the DNA repair gene brca2. 8 DSB repair is also coordinated and tightly coupled with dynamic changes in chromatin architecture that facilitate the homology search and stabilize interactions between homologous DNA sequences.…”

Analysis of the mechanism by which dADA2 factors contribute to the specificity of dSAGA and dATAC histone acetyltransferase complexes

“…Sug gene is highly induced in sugar-fed larvae in the fat body and parts of the midgut (Zinke et al, 2002). Cnc gene affects cell proliferation and development (Deng and Kerppola, 2013) while Hus 1-like gene is essential for the activation of the meiotic checkpoint (Abdu et al, 2007). The expression of Frost gene is essential for cold tolerance in Drosophila melanogaster and may play an important role in thermal adaptation (Colinet et al, 2010).…”