Biard-Roche J, Gorka C, Lawrence J J
EMBO J. 1982;1(12):1487-92. doi: 10.1002/j.1460-2075.1982.tb01344.x.
A previous study on the distribution of histone H1 subfractions in chromatin suggested that these proteins differ in the protection they confer to DNA. To elucidate further this suggestion, reconstitution experiments were carried out with purified H1 subfractions (H1-1, H1-2, H1o) and H1-depleted chromatin. We have studied the structural properties of H1o as compared to those of other H1 fractions by electrophoretic analysis of DNA and mononucleosomes obtained after micrococcal nuclease digestion, thermal denaturation, and electron microscopy. The three fractions studied reassociate to H1-depleted chromatin. However, differences in the extent of DNA protection are observed between H1o and the other fractions: H1o induces a more rapid degradation of long oligomers into mononucleosomes; these mononucleosomes bearing H1o only, have a greater electrophoretic mobility; furthermore, thermal denaturation shows that a small fraction of DNA is less efficiently protected by H1o than by the other fractions. Electron microscopy, on the other hand, shows that these differences are not due to areas of chromatin devoid of H1o in the reconstitute and that the reconstituted samples are able, under proper ionic conditions, to refold in a higher-order structure.
先前一项关于染色质中组蛋白H1亚组分分布的研究表明，这些蛋白质在对DNA的保护作用上存在差异。为了进一步阐明这一观点，我们用纯化的H1亚组分（H1-1、H1-2、H1o）和去除H1的染色质进行了重组实验。我们通过对微球菌核酸酶消化、热变性和电子显微镜观察后得到的DNA和单核小体进行电泳分析，研究了H1o与其他H1组分相比的结构特性。所研究的这三个组分都能与去除H1的染色质重新结合。然而，在H1o与其他组分之间观察到了DNA保护程度的差异：H1o能使长链寡聚体更快地降解为单核小体；这些仅带有H1o的单核小体具有更大的电泳迁移率；此外，热变性表明，与其他组分相比，一小部分DNA受H1o的保护效率较低。另一方面，电子显微镜显示，这些差异并非由于重组染色质中存在不含H1o的区域，并且在适当的离子条件下，重组样品能够重新折叠成更高阶的结构。
