Spain T A, Sun R, Miller G
Department of Epidemiology, Department of Public Health, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut 06520, USA.
Virology. 1997 Oct 13;237(1):137-47. doi: 10.1006/viro.1997.8770.
EBV DNA contains G-rich, repeat regions that are involved in rearrangement and recombination events including terminal repeat (TR) processing and the EBNA-2 deletion in the EBV strain P3HR-1. Cellular proteins, called terminal or tandem repeat binding proteins (TRBPs), recognize sequences at the junctions of these recombination events. In this study, using antibody supershift assays and expression of recombinant proteins, we show that Sp1 and Sp3 are the sequence-specific components of TRBP and that Ku is the nonspecific binding component. Sp1 binds other recombinogenic regions of EBV DNA, but Sp3 does not bind to the large internal repeat. The sequence GGGGTGGGG, a low affinity site for Sp1 and Sp3, is the minimal binding site within terminal repeat binding site 1 (TRBS1). However, 3' flanking sequences in the sequence GGGGTGGGGCATGGGG augment binding of Sp1 and Sp3 so that their affinity of binding is increased approximately twofold relative to a classical high-affinity Sp1 site. EBV lytic cycle induction does not alter the abundance or binding activity of any of the three identified components of TRBP. Sp1 and Sp3 may act in trans to promote EBV terminal repeat processing and possibly other viral and cellular recombination events.
EBV DNA含有富含G的重复区域，这些区域参与重排和重组事件，包括末端重复序列（TR）加工以及EBV毒株P3HR - 1中的EBNA - 2缺失。细胞蛋白，即末端或串联重复结合蛋白（TRBP），可识别这些重组事件连接处的序列。在本研究中，通过抗体超迁移分析和重组蛋白表达，我们表明Sp1和Sp3是TRBP的序列特异性成分，而Ku是非特异性结合成分。Sp1可结合EBV DNA的其他重组区域，但Sp3不与大的内部重复序列结合。序列GGGGTGGGG是Sp1和Sp3的低亲和力位点，是末端重复结合位点1（TRBS1）内的最小结合位点。然而，序列GGGGTGGGGCATGGGG中的3'侧翼序列增强了Sp1和Sp3的结合，使其结合亲和力相对于经典的高亲和力Sp1位点增加了约两倍。EBV裂解周期诱导不会改变TRBP的三种已鉴定成分中任何一种的丰度或结合活性。Sp1和Sp3可能通过反式作用促进EBV末端重复序列加工以及可能的其他病毒和细胞重组事件。
