Someya A, Tanaka N, Okuyama A
Molecular Biology Research Laboratories, Banyu Tsukuba Research Institute, Japan.
Exp Cell Res. 1995 Jan;216(1):280-3. doi: 10.1006/excr.1995.1035.
When sperm nuclei were added to Xenopus S phase (activated) egg extracts pretreated with a serine/threonine protein phosphatase inhibitor, calyculin A, a density substitution experiment showed that newly synthesized sperm DNA migrated in two peaks, heavy-light DNA and heavy-heavy DNA, only in the presence of calyculin A and that the total DNA replication activity was activated. In contrast, the addition of calyculin A to S phase extracts about 30 min after addition of sperm nuclei had no effect on DNA replication activity. Calyculin A clearly prevented the decline of Replication Licensing Factor activity during S phase. These results imply that the occurrence of some rereplication and the activation of DNA replication by calyculin A in activated extracts may be due to the inhibition of inactivation of licensed sites of initiation or the increase in the number of the initiation sites of DNA replication because of lack of the fall in Licensing Factor activity during S phase.
当将精子细胞核添加到用丝氨酸/苏氨酸蛋白磷酸酶抑制剂花萼海绵诱癌素A预处理的非洲爪蟾S期（激活的）卵提取物中时，密度置换实验表明，仅在存在花萼海绵诱癌素A的情况下，新合成的精子DNA以两个峰迁移，即重-轻DNA和重-重DNA，并且总DNA复制活性被激活。相比之下，在添加精子细胞核约30分钟后向S期提取物中添加花萼海绵诱癌素A对DNA复制活性没有影响。花萼海绵诱癌素A明显阻止了S期期间复制许可因子活性的下降。这些结果表明，在激活的提取物中，花萼海绵诱癌素A导致的一些再复制的发生和DNA复制的激活可能是由于起始许可位点失活的抑制，或者是由于S期期间许可因子活性没有下降导致DNA复制起始位点数量增加。
