Jang Janet K, Sherizen Dalia E, Bhagat Rajal, Manheim Elizabeth A, McKim Kim S
Waksman Institute and Department of Genetics, Rutgers, the State University of New Jersey, 190 Frelinghuysen RD, Piscataway, New Jersey 08854-8020, USA.
J Cell Sci. 2003 Aug 1;116(Pt 15):3069-77. doi: 10.1242/jcs.00614. Epub 2003 Jun 10.
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 (gamma-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 gamma-HIS2AV foci in c(3)G mutants, which fail to assemble synaptonemal complex, suggesting that there may be both synaptonemal complex-dependent and synaptonemal complex-independent mechanisms for generating double-strand breaks. Furthermore, mutations in Drosophila Rad54 (okr) and Rad51 (spnB) homologs cause delayed and prolonged gamma-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.
联会复合体形成（联会）与双链断裂形成（重组起始）之间的关系在不同生物中有所不同。虽然双链断裂的产生对于酿酒酵母和小鼠的正常联会是必需的，但对于果蝇和秀丽隐杆线虫的联会并非必要。为了研究果蝇减数分裂过程中双链断裂形成的时间和要求，我们使用了一种抗体，该抗体可识别双链断裂位点处的组蛋白修饰，即HIS2AV的磷酸化（γ-HIS2AV）。我们的结果支持双链断裂形成发生在联会之后的假说。有趣的是，我们在无法组装联会复合体的c(3)G突变体中检测到低数量（野生型的10-25%）的γ-HIS2AV焦点，这表明可能存在依赖联会复合体和不依赖联会复合体的双链断裂产生机制。此外，果蝇Rad54（okr）和Rad51（spnB）同源物的突变导致γ-HIS2AV染色延迟和延长，这表明在这些突变体中双链断裂修复延迟但未消除。修复蛋白的募集与磷酸化之间也可能存在相互作用。
