A HUMAN 200-KDA PROTEIN BINDS SELECTIVELY TO DNA FRAGMENTS CONTAINING G.T MISMATCHES
A HUMAN 200-KDA PROTEIN BINDS SELECTIVELY TO DNA FRAGMENTS CONTAINING G.T MISMATCHES
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DOI：
10.1073/pnas.85.23.8860
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发表时间：
1988-12-01
影响因子：
11.1
通讯作者：
RUDKIN, BB
中科院分区：
文献类型：
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作者：
JIRICNY, J;HUGHES, M;RUDKIN, BB
G. C. T错配是"静息"哺乳动物DNA中可能出现的唯一错配类型（通过5-甲基胞嘧啶的自发水解脱氨基作用），在体内被高效纠正，并且大部分纠正为G. C.我们确定了一种蛋白质因子，存在于HeLa细胞提取物中，它选择性地与含有这种错配的DNA底物结合。凝胶过滤层析和UV交联实验表明，部分纯化的蛋白质具有200 kDa的表观分子量。它与G. cnt. T错配对的结合不受错配侧翼序列的影响，但错配本身或其紧邻区域的鸟嘌呤甲基化会破坏蛋白质-DNA复合物的形成。该蛋白质似乎缺乏内切和外切核酸酶活性，并且不需要镁、锌或ATP来结合。我们讨论了这种蛋白质在修复途径中的可能作用，这有助于哺乳动物细胞对抗5-甲基胞嘧啶水解脱氨基的致突变作用。
G.cntdot.T mispairs, the sole mismatch type that can arise in "resting" mammalian DNA (through spontaneous hydrolytic deamination of 5-methylcytosine) are corrected in vivo with high efficiency and mostly to a G.cntdot.C. We identified a protein factor, present in HeLa cell extracts, that binds selectively to DNA substrates containing this mismatch. The partially purified protein was shown by gel-filtration chromatography and UV cross-linking experiments to have an apparent molecular mass of 200 kDa. Its binding to G.cntdot.T mispairs was not influenced by sequences flanking the mismatch, but methylation of guanines either within the mismatch itself or in its immediate vicinity abolished the formation of the protein-DNA complex. The protein appears to lack both endo- and exonuclease activities and requires neither magnesium nor zinc nor ATP for binding. We discuss the possible role of this protein in a repair pathway, which helps mammalian cells counter the mutagenic effect of the hydrolytic deamination of 5-methylcytosine.