LeBowitz J H, Clerc R G, Brenowitz M, Sharp P A
Center for Cancer Research, Massachusetts Institute of Technology, Cambridge 02139.
Genes Dev. 1989 Oct;3(10):1625-38. doi: 10.1101/gad.3.10.1625.
Recombinant proteins derived from the cloned human oct-2 gene were used to investigate cooperative binding by Oct-2 to adjacent DNA-binding sites. Oct-2, a B-cell-specific transcription factor, binds tightly to the octamer sequence in immunoglobulin promoters. A second apparently unrelated consensus sequence in heavy chain promoters, the heptamer site, also is recognized by the Oct-2 protein but with 1000-fold lower affinity. Simultaneous occupancy of both the octamer and heptamer sites is favored by cooperative interactions. The heptamer site is probably recognized by the same binding surface in the Oct-2 protein as the octamer site and thus is conserved as a lower-affinity binding site. This permits the immunoglobulin promoter to respond to a much broader range of levels of Oct-2 protein. Substitution of prototype octamer sequences for heptamer sequences yields a probe with two octamer sites spaced by 2 nucleotides, which also binds Oct-2 protein cooperatively. Only the POU domain in the Oct-2 protein is required for this cooperative interaction. Similar protein-protein interactions between bound Oct-2 proteins may promote promoter-enhancer synergism in the heavy chain gene.
从克隆的人类oct-2基因衍生而来的重组蛋白被用于研究Oct-2与相邻DNA结合位点的协同结合。Oct-2是一种B细胞特异性转录因子，它紧密结合免疫球蛋白启动子中的八聚体序列。重链启动子中另一个明显不相关的共有序列，即七聚体位点，也能被Oct-2蛋白识别，但亲和力低1000倍。八聚体位点和七聚体位点的同时占据受到协同相互作用的促进。七聚体位点可能被Oct-2蛋白中与八聚体位点相同的结合表面识别，因此作为低亲和力结合位点而被保留。这使得免疫球蛋白启动子能够对更广泛水平的Oct-2蛋白做出反应。用原型八聚体序列替代七聚体序列会产生一个探针，其两个八聚体位点相隔2个核苷酸，该探针也能与Oct-2蛋白协同结合。这种协同相互作用仅需要Oct-2蛋白中的POU结构域。结合的Oct-2蛋白之间类似的蛋白质-蛋白质相互作用可能促进重链基因中的启动子-增强子协同作用。
