PARTICIPATION OF OLIGOMERIZATION THROUGH C-TERMINAL D-DOMAIN REGION OF SP1 IN DNA-BINDING

Transcription factor Sp1 is a Cys(2)His(2)-type zinc finger protein th at specifically binds to GC-boxes on numerous viral and cellular genes . In this study, we prepared several Sp1 mutant peptides Sp1 (530-696) containing zinc finger region and the domain D, and Sp1 (530-623) con taining only zinc finger region, and then investigated the participati on of the C-terminal domain D of Spl for GC-box binding. Gel mobility shift assays demonstrate that Sp1 (530-696) evidently shows DNA-bindin g modes different from Sp1 (530-623) and that the Sp1 mutant containin g the domain D self-interacts directly. Domain D may play an important role in the synergistic activation of Sp1 by the stacking of tetramer s. A novel model for Sp1 oligomerization has also been proposed.