Schlaeger E J
Biochemistry. 1982 Jun 22;21(13):3167-74. doi: 10.1021/bi00256a021.
The transiently altered DNA-histone interaction of parental chromatin during replication was studied by micrococcal nuclease digestion. A large amount of nuclease-resistant pulse-labeled DNA and a small fraction of nonreplicating DNA are released from chromatin fragments by treatment with 0.5 M NaCl and appear as protein-free DNA. As shown by reconstitution experiments, the salt sensitivity of digested nascent chromatin is most probably a consequence of the shorter DNA fragment size (55 +/- 15 base pairs) in these complexes. This new DNA is associated with parental chromatin fragments which are structurally changed in such a way that parts of nucleosomal DNA were more susceptible to nuclease attack. The core histones of these particles are probably not distinct from those of salt-stable nucleosomes. However, histone H1 and probably high-mobility group proteins appear to be more weakly bound during replication as shown by electrophoresis under nondenaturing conditions. The results agree with the assumption that the transient alteration of nucleosomal conformation describes a state in which DNA could be replicated without leaving the associated core histone complexes. A possible attachment of pulse-labeled chromatin with nuclear matrix is discussed.
通过微球菌核酸酶消化研究了复制过程中亲代染色质的DNA-组蛋白相互作用的瞬时变化。用0.5M NaCl处理染色质片段后，可释放出大量抗核酸酶脉冲标记的DNA和一小部分非复制性DNA，并呈现为无蛋白质的DNA。重建实验表明，消化后的新生染色质对盐的敏感性很可能是这些复合物中DNA片段较短（55±15个碱基对）的结果。这种新DNA与亲代染色质片段相关，亲代染色质片段的结构发生了变化，使得核小体DNA的部分区域更容易受到核酸酶的攻击。这些颗粒的核心组蛋白可能与盐稳定核小体的核心组蛋白没有区别。然而，如非变性条件下的电泳所示，组蛋白H1以及可能的高迁移率族蛋白在复制过程中似乎结合较弱。结果与以下假设一致，即核小体构象的瞬时变化描述了一种DNA可以在不离开相关核心组蛋白复合物的情况下进行复制的状态。讨论了脉冲标记染色质与核基质的可能附着。
