Interaction of Sp1 with the growth- and cell cycle-regulated transcription factor E2F.

摘要: Within the region around 150 bp upstream of initiation codon, which was previously shown to suffice for growth-regulated expression, murine thymidine kinase gene carries a single binding site transcription factor Sp1; about 10 downstream this site, there is motif E2F. The latter protein appears be responsible growth regulation promoter. Mutational inactivation either Sp1 or E2F almost completely abolishes promoter activity, suggesting that two factors interact directly in delivering an activation signal basic machinery. This verified by demonstrating with use glutathione S-transferase fusion proteins and bind each other vitro. For interaction, C-terminal part N terminus E2F1, domain also present E2F2 E2F3 but absent E2F4 E2F5, were essential. Accordingly, E2F1 not E2F5 found sp1 Coimmunoprecipitation experiments showed complexes exist vivo, it estabilished distance between sites critical optimal activity. Finally, vivo footprinting indicated both are occupied throughout cell cycle. Mutation abolished may indicate cooperative chromatin-organized DNA. Our data line hypothesis functions as growth- cycle regulated tethering