Ishimi Y, Komamura Y, You Z, Kimura H
Mitsubishi Kasei Institute of Life Sciences, 11 Minamiooya, Machida, Tokyo 194, Japan.
J Biol Chem. 1998 Apr 3;273(14):8369-75. doi: 10.1074/jbc.273.14.8369.
Minichromosome maintenance (MCM) proteins play an essential role in eukaryotic DNA replication and bind to chromatin before the initiation of DNA replication. We reported that MCM protein complexes consisting of MCM2, -4, -6, and -7 bind strongly to a histone-Sepharose column (Ishimi, Y., Ichinose, S., Omori, A., Sato, K., and Kimura, H. (1996) J. Biol. Chem. 271, 24115-24122). Here, we have analyzed this interaction at the molecular level. We found that among six mouse MCM proteins, only MCM2 binds to histone; amino acid residues 63-153 are responsible for this binding. The region required for nuclear localization of MCM2 was mapped near this histone-binding domain. Far-Western blotting analysis of truncated forms of H3 histone indicated that amino acid residues 26-67 of H3 histone are required for binding to MCM2. We have also shown that mouse MCM2 can inhibit the DNA helicase activity of the human MCM4, -6, and -7 protein complex. These results suggest that MCM2 plays a different role in the initiation of DNA replication than the other MCM proteins.
微小染色体维持（MCM）蛋白在真核生物DNA复制中起关键作用，并在DNA复制起始前与染色质结合。我们报道过，由MCM2、-4、-6和-7组成的MCM蛋白复合物能与组蛋白琼脂糖柱紧密结合（石见义明、市之濑史、大森明、佐藤健和木村博，（1996年）《生物化学杂志》271卷，24115 - 24122页）。在此，我们在分子水平上分析了这种相互作用。我们发现，在六种小鼠MCM蛋白中，只有MCM2能与组蛋白结合；氨基酸残基63 - 153负责这种结合。MCM2核定位所需区域定位在该组蛋白结合域附近。对截短形式的H3组蛋白进行Far - Western印迹分析表明，H3组蛋白的氨基酸残基26 - 67是与MCM2结合所必需的。我们还表明，小鼠MCM2能抑制人MCM4、-6和-7蛋白复合物的DNA解旋酶活性。这些结果表明，MCM2在DNA复制起始过程中发挥的作用与其他MCM蛋白不同。
