The Oct-2 protein binds cooperatively to adjacent octamer sites.
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.
LeBowitz
J H
JH
Center for Cancer Research, Massachusetts Institute of Technology, Cambridge 02139.
Clerc
R G
RG
Brenowitz
M
M
Sharp
P A
PA
D001483:Base Sequence; D001665:Binding Sites; D004247:DNA / Q000378:metabolism*; D015342:DNA Probes; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005803:Genes, Immunoglobulin; D006801:Humans; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D050813:Octamer Transcription Factor-2; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism; D014157:Transcription Factors; D014158:Transcription, Genetic
D015342:DNA Probes; D004268:DNA-Binding Proteins; D050813:Octamer Transcription Factor-2; C058435:POU2F2 protein, human; D011994:Recombinant Proteins; D014157:Transcription Factors; D004247:DNA