Relationship of DNA double-strand breaks to synapsis in Drosophila

Abstract

The relationship between synaptonemal complex formation (synapsis) and double-strand break formation (recombination initiation) differs between organisms. Although double-strand break creation is required for normal synapsis in Saccharomyces cerevisiae and the mouse, it is not necessary for synapsis in Drosophila and Caenorhabditis elegans. To investigate the timing of and requirements for double-strand break formation during Drosophila meiosis, we used an antibody that recognizes a histone modification at double-strand break sites, phosphorylation of HIS2AV (γ-HIS2AV). Our results support the hypothesis that double-strand break formation occurs after synapsis. Interestingly, we detected a low (10-25% of wildtype) number of γ-HIS2AV foci in c(3)G mutants, which fail to assemble synaptonemal complex, suggesting that there may be both synaptonemal complexdependent and synaptonemal complex-independent mechanisms for generating double-strand breaks. Furthermore, mutations in Drosophila Rad54 (okr) and Rad51 (spnB) homologs cause delayed and prolonged γ-HIS2AV staining, suggesting that double-strand break repair is delayed but not eliminated in these mutants. There may also be an interaction between the recruitment of repair proteins and phosphorylation.

Multiple Barriers to Nonhomologous DNA End Joining During Meiosis inDrosophila

“…The following mutations were used and have been previously described: spn-A 1 , spn-A 093 , spn-B BU , and spn-D 150 (Ghabrial et al 1998;Abdu et al 2003;Jang et al 2003;Staeva-Vieira et al 2003), mei-218 1 , mei-218 6 (Carpenter and Sandler 1974;McKim et al 1996), rec 1 and rec 2 (Blanton et al 2005), and lig4 57 (Gorski et al 2003;Romeijn et al 2005). Experiments with rec were done with rec 1 /rec 2 heterozygotes.…”

“…Thus, mutation of Drosophila Rad51, spn-A, and its paralogs spn-D and spn-B, block meiotic DSB repair and accumulate DSBs into late stages of pachytene, as detected by an antibody to the phosphorylated form of H2AV (Ghabrial et al 1998;Ghabrial and Schupbach 1999;Abdu et al 2003;Jang et al 2003;Staeva-Vieira et al 2003;Mehrotra and McKim 2006). spn-D and spn-B encode orthologs of RAD51C and XRCC3, respectively, which are believed to function as a heterodimer in mammalian cells to promote DSB repair by homologous recombination (HR) (Kurumizaka et al 2001;Abdu et al 2003;Sung et al 2003;Radford and Sekelsky 2004).…”

A Maternal Screen for Genes Regulating Drosophila Oocyte Polarity Uncovers New Steps in Meiotic Progression

“…Several cells in each cyst enter meiotic prophase, condense their chromosomes, form synapses between the homologs, and repair double-strand breaks (DSB) in the DNA, but only one cystocyte reaches the full pachytene state (Carpenter 1979;Hawley 2001, 2004;Jang et al 2003). Mutations in meiotic genes, such as the DSB repair genes okra/dRad54 (okr) and spindle-A/dRad51 (spn-A), delay this restriction.…”

Meiotic Transverse Filament Proteins: Essential for Crossing Over

“…These mutants still initiate meiotic recombination (by induction of DNA double-strand breaks) (de Vries et al, 2005;Colaia´covo et al, 2003;Jang et al, 2003;Storlazzi et al, 1996), and align homologous chromosomes (de Vries et al, 2005; reviewed by Page and Hawley, 2003). However, in all four analyzed species crossover formation is affected in TF-deficient mutants (reviewed by Page and Figure 1.…”