The binding of SNAPc to the PSE is stabilized by a number of cooperative interactions with other members of the transcription initiation complex including Oct-1, TBP, and Brf2.

The binding of SNAPc to the core promoter is stabilized by a direct protein-protein contact with the Oct-1 POU domain.

SNAPc does not bind very efficiently to the PSE on its own. It contains a damper of DNA binding that resides within the C-terminal two thirds of SNAP190 and/or SNAP45, because a subcomplex of SNAPc (mini-SNAPc) lacking these sequences binds much more efficiently to DNA than complete SNAPc (Mittal et al., 1999). The damper within SNAPc is deactivated, probably through a conformational change, by a direct protein-protein contact with the Oct-1 POU domain. The transcription initiation complex is illustrated in Figure 6. The protein-protein contact between the Oct-1 POU domain and SNAPc involves a glutamic acid at position 7 within the Oct-1 POUS domain and a lysine at position 900 within SNAP190, which are symbolized in Figure 6 by small triangles (Ford et al., 1998; Hovde et al., 2002; Mittal et al., 1999). The octamer sequence within the DSE and the PSE are separated by more than 150 base pairs, but the direct protein-protein contact is rendered possible by the presence of a positioned nucleosome between the DSE and the PSE, which, as shown in the figure, probably brings into close proximity the Oct-1 POU domain and SNAPc (Stunkel et al., 1997; Zhao et al., 2001).