Cheng L, Kelly T J
Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Cell. 1989 Nov 3;59(3):541-51. doi: 10.1016/0092-8674(89)90037-8.
SV40 DNA replication in vivo is greatly stimulated by cis-acting transcriptional elements. We studied a model viral chromosome containing a single binding site for the cellular transcriptional activator, nuclear factor I (NF-I/CTF), located adjacent to the replication origin. The presence of the NF-I recognition site increased replication efficiency over 20-fold in vivo. Purified NF-I had little effect on the replication efficiency in the standard SV40 cell-free system when the template was introduced as naked DNA. However, NF-I specifically prevented the repression of DNA replication that occurred when the template was preassembled into chromatin. Our data support a model in which the binding of a transcriptional activator perturbs the local distribution of nucleosomes, thereby increasing the accessibility of the origin region.
在体内，顺式作用转录元件可极大地刺激SV40 DNA的复制。我们研究了一种模型病毒染色体，该染色体在复制起点附近含有一个细胞转录激活因子核因子I（NF-I/CTF）的单一结合位点。NF-I识别位点的存在使体内复制效率提高了20多倍。当模板以裸露DNA形式引入时，纯化的NF-I对标准的无细胞SV40系统中的复制效率几乎没有影响。然而，NF-I可特异性地阻止当模板预组装成染色质时发生的DNA复制抑制。我们的数据支持这样一种模型，即转录激活因子的结合扰乱了核小体的局部分布，从而增加了起点区域的可及性。
