Ira G, Svetlova E, Filipski J
Laboratoire de Mutagénèse. Institut J. Monod. 2, place Jussieu, Tour 43, 75251 Paris, France.
Nucleic Acids Res. 1998 May 15;26(10):2415-9. doi: 10.1093/nar/26.10.2415.
Meiotic recombination in the yeast Saccharomyces cerevisiae is initiated by double-strand breaks (DSB) in chromosomal DNA. These DSB, which can be mapped in the rad 50S mutant yeast strain, are caused by a topoisomerase II-like enzyme, the protein Spo11. Evidence suggests that this protein is located in the axial element of the meiotic chromosome which implies that the DSB are located in these chromosomes in the vicinity of the bases of the DNA loops. We have found that in the yeast artificial chromosomes carrying human DNA, at the level of resolution obtained by pulsed field gel electrophoresis (PFGE), the meiotic DSB in the diploid yeast are co-localized with the DNase I hypersensitive sites (HS) in a haploid strain of yeast. These HS are located close to sequences which, under stress, have the potential to form secondary structures containing unpaired nucleotides. Clusters of such sequences could be a hallmark of the bases of the chromatin loops.
酿酒酵母中的减数分裂重组由染色体DNA中的双链断裂（DSB）引发。这些DSB可在rad 50S突变酵母菌株中定位，是由一种拓扑异构酶II样酶Spo11蛋白引起的。有证据表明，该蛋白位于减数分裂染色体的轴向元件中，这意味着DSB位于这些染色体中DNA环基部附近。我们发现，在携带人类DNA的酵母人工染色体中，在脉冲场凝胶电泳（PFGE）获得的分辨率水平上，二倍体酵母中的减数分裂DSB与单倍体酵母菌株中的DNase I超敏位点（HS）共定位。这些HS位于靠近在应激条件下有可能形成含有未配对核苷酸的二级结构的序列附近。此类序列簇可能是染色质环基部的标志。
