Frank O, Schwanbeck R, Wiśniewski J R
III. Zoologisches Institut-Entwicklungsbiologie, Universität Göttingen, Humboldtallee 34A, 37073 Göttingen, Germany.
J Biol Chem. 1998 Aug 7;273(32):20015-20. doi: 10.1074/jbc.273.32.20015.
The high mobility group proteins I and Y (HMGI/Y) are abundant components of chromatin. They are thought to derepress chromatin, affect the assembly and activity of the transcriptional machinery, and associate with constitutive heterochromatin during mitosis. HMGI/Y protein molecules contain three potential DNA-binding motifs (AT-hooks), but the extent of contacts between DNA and the entire protein has not been determined. We have used a protein-footprinting procedure to map regions of the Chironomus HMGI protein molecule that are involved in contacts with DNA. We find that in the presence of double-stranded DNA all AT-hook motifs are protected against hydroxyl radical proteolysis. In contrast, only two motifs were protected in the presence of four-way junction DNA. Large regions that flank the AT-hook motifs were found to be strongly protected against proteolysis in complexes with interferon-beta promoter DNA, suggesting amino acid residues outside the AT-hooks considerably contribute to DNA binding.
高迁移率族蛋白I和Y（HMGI/Y）是染色质的丰富组成成分。它们被认为可使染色质去抑制，影响转录机器的组装和活性，并在有丝分裂期间与组成型异染色质相关联。HMGI/Y蛋白分子包含三个潜在的DNA结合基序（AT钩），但DNA与整个蛋白质之间的接触程度尚未确定。我们使用了一种蛋白质足迹法来绘制摇蚊HMGI蛋白分子中与DNA接触的区域。我们发现，在双链DNA存在的情况下，所有AT钩基序都受到保护，免受羟基自由基蛋白水解作用。相比之下，在四链连接DNA存在的情况下，只有两个基序受到保护。在与干扰素-β启动子DNA形成的复合物中，发现AT钩基序两侧的大片区域受到强烈保护，免受蛋白水解作用，这表明AT钩之外的氨基酸残基对DNA结合有很大贡献。
