由存在于组蛋白H1 C末端的含SPKK八肽重复基序介导的DNA和染色质凝聚。

Condensation of DNA and chromatin by an SPKK-containing octapeptide repeat motif present in the C-terminus of histone H1.

作者信息

Khadake J R, Rao M R

机构信息

Department of Biochemistry, Indian Institute of Science, Bangalore, India.

出版信息

Biochemistry. 1997 Feb 4;36(5):1041-51. doi: 10.1021/bi961617p.

DOI:10.1021/bi961617p

PMID:9033394

Abstract

Several DNA binding motifs have been described in the C-terminus of histone H1 (Churchill & Travers, 1991), of these the S/TPKK repeat (Suzuki, 1989) often occurs as a part of an octapeptide repeat of the type XTPKKXKK. We have studied in detail the DNA and chromatin condensing properties of a consensus octapeptide KSPKKAKK (8 mer) present in many histone H1 subtypes and its imperfect repeat ATPKKSTKKTPKKAKK (16 mer TPKK) as it occurs in the C-terminus of rat histone H1d. The 16 mer TPKK peptide containing two S/TPKK motifs was able to condense both rat oligonucleosomal (2-5 kbp) DNA and histone H1-depleted chromatin as revealed by circular dichroism spectroscopy. The 8 mer peptide, however, was unable to condense either the DNA or the histone H1-depleted chromatin. Both the 8 mer peptide and the 16 mer TPKK peptide displaced distamycin A from the drug-DNA complex, although with different efficiency, indicating that while these two peptides could bind DNA, only the 16 mer (TPKK) peptide could bring about condensation of DNA and histone H1-depleted chromatin. A mutant 16 mer (TAKK) peptide wherein two proline residues are replaced by alanine, was ineffective in bringing about condensation of both DNA and histone H1-depleted chromatin. These results suggest that the two beta-turn structures present in the 16 mer (TPKK) peptide could be important in facilitating binding to different regions of duplex DNA thereby bringing about close packing and condensation. The condensation property of the 16 mer (TPKK) peptide was very similar to that of histone H1 in terms of (a) its preference for AT rich DNA, (b) cooperativity of condensation, and (c) salt dependence of condensation. The 16 mer (TPKK) peptide, but not the 8 mer peptide or the 16 mer (TAKK) peptide, could form complexes with a polynucleosomal 5S DNA core resulting in retarded mobility similar to the complexes formed with histone H1 on agarose gel electrophoresis.

摘要

在组蛋白H1的C末端已发现了几种DNA结合基序（丘吉尔和特拉弗斯，1991年），其中S/TPKK重复序列（铃木，1989年）常作为XTPKKXKK型八肽重复序列的一部分出现。我们详细研究了许多组蛋白H1亚型中存在的共有八肽KSPKKAKK（8聚体）及其不完美重复序列ATPKKSTKKTPKKAKK（16聚体TPKK，存在于大鼠组蛋白H1d的C末端）的DNA和染色质凝聚特性。圆二色光谱显示，含有两个S/TPKK基序的16聚体TPKK肽能够凝聚大鼠寡核小体（2 - 5千碱基对）DNA和组蛋白H1缺失的染色质。然而，8聚体肽既不能凝聚DNA，也不能凝聚组蛋白H1缺失的染色质。8聚体肽和16聚体TPKK肽都能从药物 - DNA复合物中取代偏端霉素A，尽管效率不同，这表明虽然这两种肽都能结合DNA，但只有16聚体（TPKK）肽能引起DNA和组蛋白H1缺失染色质的凝聚。一种突变的16聚体（TAKK）肽，其中两个脯氨酸残基被丙氨酸取代，在引起DNA和组蛋白H1缺失染色质的凝聚方面无效。这些结果表明，16聚体（TPKK）肽中存在的两个β - 转角结构可能在促进与双链DNA不同区域的结合从而实现紧密堆积和凝聚方面很重要。16聚体（TPKK）肽的凝聚特性在以下方面与组蛋白H1非常相似：（a）对富含AT的DNA的偏好，（b）凝聚的协同性，以及（c）凝聚的盐依赖性。16聚体（TPKK）肽，而不是8聚体肽或16聚体（TAKK）肽，能与多核小体5S DNA核心形成复合物，导致迁移率减慢，类似于在琼脂糖凝胶电泳上与组蛋白H1形成的复合物。