Moore S C, Ausió J
Department of Biochemistry and Microbiology, University of Victoria, British Columbia, Canada.
Biochem Biophys Res Commun. 1997 Jan 3;230(1):136-9. doi: 10.1006/bbrc.1996.5903.
We have characterized the hydrodynamic behavior of nucleosome arrays in which the N- and C-terminal "tails" of the histone H2A-H2B and H3-H4 domains have been selectively removed by digestion with immobilized trypsin. The sedimentation coefficient of the polynucleosome fibers lacking the histone H2A-H2B tails exhibited a salt dependence close to that of the non-trypsinized nucleosome arrays. In contrast, the salt-dependent behavior of the H3-H4-trypsinized polynucleosome fibers was found to be closer to that observed for the nucleosome arrays on which all the histones were trypsinized. This indicates that the N- and C-terminal domains of histones H3-H4 play a major role in the folding of the chromatin fiber. Magnesium titration of the polynucleosome fibers consisting of these trypsinized histone octamer hybrids at low ionic strength indicates that the histone H3-H4 tails also play an important role in the association of the polynucleosome fibers. These findings suggest that, after linker histones (histones of the H1 family), the tails of the histone H3-H4 domains are the major players in the processes that lead to the intra-association (folding) and inter-association of the chromatin fiber.
我们已经对核小体阵列的流体动力学行为进行了表征，其中通过固定化胰蛋白酶消化选择性去除了组蛋白H2A-H2B和H3-H4结构域的N端和C端“尾巴”。缺乏组蛋白H2A-H2B尾巴的多核小体纤维的沉降系数表现出与未用胰蛋白酶处理的核小体阵列相近的盐依赖性。相反，发现经H3-H4胰蛋白酶处理的多核小体纤维的盐依赖性行为更接近于对所有组蛋白都进行了胰蛋白酶处理的核小体阵列所观察到的行为。这表明组蛋白H3-H4的N端和C端结构域在染色质纤维的折叠中起主要作用。在低离子强度下对由这些经胰蛋白酶处理的组蛋白八聚体杂种组成的多核小体纤维进行镁滴定表明，组蛋白H3-H4尾巴在多核小体纤维的缔合中也起重要作用。这些发现表明，在连接组蛋白（H1家族的组蛋白）之后，组蛋白H3-H4结构域的尾巴是导致染色质纤维内缔合（折叠）和相互缔合过程中的主要参与者。
