Isolation of type I and II DNA topoisomerase mutants from fission yeast: single and double mutants show different phenotypes in cell growth and chromatin organization.

摘要: Abstract We have isolated mutants defective in DNA topoisomerases and an endonuclease from the fission yeast Schizosaccharomyces pombe by screening individual extracts of mutagenized cells. Two type I topoisomerase (top1) three (end1) were all viable. The double mutant top1 end1 was also viable and, its extract, Mg2+- ATP- dependent II activity could be detected. Three temperature-sensitive (ts-) having heat-sensitive (hs-) enzymes isolated, ts- marker cosegregated with hs- activity. All mutations fell one gene (top2) tightly linked to leul chromosome II. nuclear division single top2 blocked at restrictive temperature, but formation a septum not inhibited so that nucleus cut across cell plate. In contrast, rapidly arrested various stages cycle, showing strikingly altered chromatin region. may essential role compaction and/or segregation chromosomes during complement defect enzyme whose major function is maintenance organization throughout cycle.