Baur C P, Knippers R
Fakultät für Biologie, Universität Konstanz, F.R.G.
J Mol Biol. 1988 Oct 20;203(4):1009-19. doi: 10.1016/0022-2836(88)90125-8.
A 3.5 S protein, isolated from mammalian nuclei, specifically binds to DNA fragments containing the simian virus 40 (SV40) origin of replication. Two distinct nucleoprotein complexes are formed, a complex with high electrophoretic mobility carrying probably only one protein molecule, and a complex with reduced electrophoretic mobility carrying probably two protein molecules per DNA fragment. Band shift competition as well as methylation interference assays locate the binding site of the protein in the A + T-rich "late" region of the origin between SV40 nucleotides 13 and 35. The late origin binding (LOB) protein and T antigen bind simultaneously to adjacent sites in the origin. Using circularly permuted DNA fragments of identical lengths we show that the LOB protein induces pronounced bending of the origin fragment. The bending center maps at the 5' end of the adenine tract with one bound protein molecule and at the 3' end when two LOB proteins are bound to one origin fragment.
从哺乳动物细胞核中分离出的一种3.5S蛋白，能特异性结合含有猿猴病毒40（SV40）复制起点的DNA片段。形成了两种不同的核蛋白复合物，一种是电泳迁移率高的复合物，可能只携带一个蛋白质分子，另一种是电泳迁移率降低的复合物，每个DNA片段可能携带两个蛋白质分子。带移竞争以及甲基化干扰试验将该蛋白的结合位点定位在SV40核苷酸13至35之间富含A+T的复制起点“晚期”区域。晚期起点结合（LOB）蛋白和T抗原同时结合在复制起点的相邻位点。使用长度相同的环形置换DNA片段，我们发现LOB蛋白可诱导复制起点片段发生明显弯曲。当一个蛋白分子结合时，弯曲中心位于腺嘌呤序列的5'端；当两个LOB蛋白结合到一个复制起点片段时，弯曲中心位于3'端。
