新生核小体DNA重复长度的缩短是通过在体内复制染色质产生的。
Reduced repeat length of nascent nucleosomal DNA is generated by replicating chromatin in vivo.
作者信息
Jakob K M, Ben Yosef S, Tal I
出版信息
Nucleic Acids Res. 1984 Jun 25;12(12):5015-24. doi: 10.1093/nar/12.12.5015.
Micrococcal nuclease digestion of nuclei from sea urchin embryos revealed transient changes in chromatin structure which resulted in a reduction in the repeat length of nascent chromatin DNA as compared with bulk DNA. This was considered to be entirely the consequence of in vivo events at the replication fork (Cell 14, 259, 1978). However, a micrococcal nuclease-generated sliding of nucleosome cores relative to nascent DNA, which might account for the smaller DNA fragments, was not excluded. In vivo [3H]thymidine pulse-labeled nuclei were fixed with a formaldehyde prior to micrococcal nuclease digestion. This linked chromatin proteins to DNA and thus prevented any in vitro sliding of histone cores. All the nascent DNAs exhibiting shorter repeat lengths after micrococcal nuclease digestion, were resolved at identical mobilities in polyacrylamide gels of DNA from fixed and unfixed nuclei. We conclude that these differences in repeat lengths between nascent and bulk DNA was generated in vivo by changes in chromatin structure during replication, rather than by micrococcal nuclease-induced sliding of histone cores in vitro.
用微球菌核酸酶消化海胆胚胎的细胞核，发现染色质结构发生了短暂变化，与总体DNA相比，新生染色质DNA的重复长度缩短。这被认为完全是复制叉处体内事件的结果（《细胞》14卷，259页，1978年）。然而，并未排除微球菌核酸酶导致核小体核心相对于新生DNA滑动的可能性，这种滑动可能是较小DNA片段产生的原因。在微球菌核酸酶消化之前，用甲醛固定体内经[³H]胸腺嘧啶脉冲标记的细胞核。这将染色质蛋白与DNA连接起来，从而防止了组蛋白核心在体外的任何滑动。微球菌核酸酶消化后，所有显示重复长度较短的新生DNA，在固定和未固定细胞核的DNA聚丙烯酰胺凝胶中，迁移率相同。我们得出结论，新生DNA与总体DNA之间重复长度的这些差异是在复制过程中由染色质结构的变化在体内产生的，而不是由微球菌核酸酶在体外诱导的组蛋白核心滑动产生的。
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