Zhang L H, Mui S C, Todt J C, Strauss P R
Proc Natl Acad Sci U S A. 1986 Aug;83(16):5871-4. doi: 10.1073/pnas.83.16.5871.
Detergent-soluble DNA is the fraction (2-4%) of DNA that is released into the supernate upon mild detergent lysis. It is nonmitochondrial in origin. It labels efficiently with deoxy[3H]ribonucleosides and the labeling is prevented by inhibitors of polymerase alpha and ribonucleotide reductase. In previous publications we have characterized detergent-soluble DNA from splenocytes of immunologically activated mice. In this publication we show that incorporation of [3H]thymidine into detergent-soluble DNA is prevented by pretreatment with novobiocin, 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA), and teniposide (VM26), three inhibitors of type II topoisomerases. Camptothecin, an inhibitor of type I topoisomerases, also reduces incorporation of [3H]thymidine but only to 50% of control levels. In addition to affecting incorporation of [3H]thymidine, preincubation with the topoisomerase II inhibitors m-AMSA and VM26 alters the amount of DNA recovered in the detergent-soluble fraction. At low concentrations of m-AMSA the amount of detergent-soluble DNA increases somewhat, whereas at higher drug concentrations a marked decrease is observed. Treatment with VM26 results in diminished amounts of DNA being released into the detergent-soluble fraction as well. However, maximal inhibition of detergent-soluble DNA release by VM26 requires the presence of camptothecin. Therefore, we suggest that topoisomerases play an important role in making a small part of lymphocyte chromatin detergent labile. Furthermore, these results are consistent with recent studies demonstrating a role for topoisomerases in yeast replication. Thus, the newly synthesized portion of detergent-soluble DNA may arise as DNA replication intermediates not yet stabilized into mature chromatin.
去污剂可溶性DNA是指在温和去污剂裂解后释放到上清液中的DNA部分（占2%-4%）。其来源是非线粒体的。它能有效地用脱氧[³H]核糖核苷进行标记，并且这种标记会被DNA聚合酶α和核糖核苷酸还原酶的抑制剂所阻止。在之前的出版物中，我们已经对免疫激活小鼠脾细胞中的去污剂可溶性DNA进行了表征。在本出版物中，我们表明，用新霉素、4'-（9-吖啶基氨基）甲磺酰基间茴香胺（m-AMSA）和替尼泊苷（VM26）这三种II型拓扑异构酶抑制剂进行预处理，可以阻止[³H]胸腺嘧啶核苷掺入去污剂可溶性DNA中。喜树碱是I型拓扑异构酶的抑制剂，它也会降低[³H]胸腺嘧啶核苷的掺入，但仅降至对照水平的50%。除了影响[³H]胸腺嘧啶核苷的掺入外，用拓扑异构酶II抑制剂m-AMSA和VM26进行预孵育会改变去污剂可溶性部分中回收的DNA量。在低浓度的m-AMSA下，去污剂可溶性DNA的量会略有增加，而在较高药物浓度下，则会观察到明显减少。用VM26处理也会导致释放到去污剂可溶性部分中的DNA量减少。然而，VM26对去污剂可溶性DNA释放的最大抑制需要喜树碱的存在。因此，我们认为拓扑异构酶在使一小部分淋巴细胞染色质对去污剂敏感方面起着重要作用。此外，这些结果与最近证明拓扑异构酶在酵母复制中起作用的研究一致。因此，去污剂可溶性DNA的新合成部分可能是作为尚未稳定成成熟染色质的DNA复制中间体出现的。
