Lu Xu, Hansen Jeffrey C
Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523-1870, USA.
J Biol Chem. 2004 Mar 5;279(10):8701-7. doi: 10.1074/jbc.M311348200. Epub 2003 Dec 10.
Linker histone binding to nucleosomal arrays in vitro causes linker DNA to form an apposed stem motif, stabilizes extensively folded secondary chromatin structures, and promotes self-association of individual nucleosomal arrays into oligomeric tertiary chromatin structures. To determine the involvement of the linker histone C-terminal domain (CTD) in each of these functions, and to test the hypothesis that the functions of this highly basic domain are mediated by neutralization of linker DNA negative charge, four truncation mutants were created that incrementally removed stretches of 24 amino acids beginning at the extreme C terminus of the mouse H1(0) linker histone. Native and truncated H1(0) proteins were assembled onto biochemically defined nucleosomal arrays and characterized in the absence and presence of salts to probe primary, secondary, and tertiary chromatin structure. Results indicate that the ability of H1(0) to alter linker DNA conformation and stabilize condensed chromatin structures is localized to specific C-terminal subdomains, rather than being equally distributed throughout the entire CTD. We propose that the functions of the linker histone CTD in chromatin are linked to the characteristic intrinsic disorder of this domain.
体外连接组蛋白与核小体阵列结合会使连接区DNA形成并列的茎状基序，稳定广泛折叠的二级染色质结构，并促进单个核小体阵列自缔合形成寡聚三级染色质结构。为了确定连接组蛋白C末端结构域（CTD）在这些功能中的作用，并检验这一高度碱性结构域的功能是通过中和连接区DNA负电荷来介导的这一假设，构建了四个截短突变体，它们从小鼠H1(0)连接组蛋白的极端C末端开始逐渐去除24个氨基酸的片段。将天然和截短的H1(0)蛋白组装到生化定义的核小体阵列上，并在有无盐的情况下进行表征，以探测一级、二级和三级染色质结构。结果表明，H1(0)改变连接区DNA构象和稳定浓缩染色质结构的能力定位于特定的C末端亚结构域，而不是均匀分布在整个CTD中。我们提出，连接组蛋白CTD在染色质中的功能与该结构域特有的内在无序性有关。
