Gidoni D, Kadonaga J T, Barrera-Saldaña H, Takahashi K, Chambon P, Tjian R
Science. 1985 Nov 1;230(4725):511-7. doi: 10.1126/science.2996137.
The 21-base pair repeat elements of the SV40 promoter contain six tandem copies of the GGGCGG hexanucleotide (GC-box), each of which can bind, with varying affinity, to the cellular transcription factor, Sp1. In vitro SV40 early RNA synthesis is mediated by interaction of Sp1 with GC-boxes I, II, and III, whereas transcription in the late direction is mediated by binding to GC-boxes III, V, and VI.
SV40启动子的21个碱基对重复元件包含六聚体核苷酸GGGCGG（GC框）的六个串联拷贝，每个拷贝都能以不同的亲和力与细胞转录因子Sp1结合。在体外，SV40早期RNA合成是由Sp1与GC框I、II和III的相互作用介导的，而晚期方向的转录是由与GC框III、V和VI的结合介导的。
