Supakar P C, Weist D, Zhang D L, Inamdar N, Zhang X Y, Khan R, Ehrlich K C, Ehrlich M
Department of Biochemistry, Tulane Medical School, New Orleans, LA 70112.
Nucleic Acids Res. 1988 Aug 25;16(16):8029-44. doi: 10.1093/nar/16.16.8029.
A DNA-binding protein from human placenta, methylated DNA-binding protein (MDBP), binds to certain DNA sequences only when they contain 5-methylcytosine (m5C) residues at specific positions. We found a very similar DNA-binding activity in nuclear extracts of rat tissues, calf thymus, human embryonal carcinoma cells, HeLa cells, and mouse LTK cells. Like human placental MDBP, the analogous DNA-binding proteins from the above mammalian cell lines formed a number of different low-electrophoretic-mobility complexes with a 14-bp MDBP-specific oligonucleotide duplex. All of these complexes exhibited the same DNA methylation specificity and DNA sequence specificity. From the extracts of rat and calf tissues, oligonucleotide protein complexes formed that also had the same specificity as human placental MDBP although they had a higher electrophoretic mobility probably due to digestion by proteases in the nuclear extracts. Although MDBP activity was found in various mammalian cell types, it was not detected in extracts of cultured mosquito cells and so may be associated only with cells with vertebrate-type DNA methylation.
一种来自人胎盘的DNA结合蛋白，即甲基化DNA结合蛋白（MDBP），仅在特定位置含有5-甲基胞嘧啶（m5C）残基时才会与某些DNA序列结合。我们在大鼠组织、小牛胸腺、人胚胎癌细胞、HeLa细胞和小鼠LTK细胞的核提取物中发现了非常相似的DNA结合活性。与人类胎盘MDBP一样，上述哺乳动物细胞系中的类似DNA结合蛋白与一个14碱基对的MDBP特异性寡核苷酸双链体形成了许多不同的低电泳迁移率复合物。所有这些复合物都表现出相同的DNA甲基化特异性和DNA序列特异性。从大鼠和小牛组织的提取物中形成的寡核苷酸蛋白复合物也具有与人类胎盘MDBP相同的特异性，尽管它们的电泳迁移率较高，这可能是由于核提取物中的蛋白酶消化所致。虽然在各种哺乳动物细胞类型中都发现了MDBP活性，但在培养的蚊子细胞提取物中未检测到，因此它可能仅与具有脊椎动物型DNA甲基化的细胞有关。
