Figure 1. Structure of E2F8.

(a) Schematic representation of the structural organization of E2F transcription factors. Key: CycA: cyclin A-binding domain; DBD: DNA-binding domain; DP-BD: DP-binding domain; TA+PB: transactivation and pocket protein-binding domains. Note that the typical E2Fs have DP-binding domains, which are replaced by a second DBD in the atypical E2Fs. (b) Superimposition of E2F8 DBD1 (pink) and DBD2 (blue) (r.m.s.d.=7.8 Å); the linker between the two DBDs is in red. (c,d) Superimpositions of E2F8 DBD1 (pink) to E2F4 (magenta) (r.m.s.d.=1.36 Å; PDB ID 1CF7) and E2F8 DBD2 (blue) to DP2 (green) (r.m.s.d.=1.9 Å; PDB ID 1CF7). The 23 amino acids of the linker close to DBD1 are folded into two α-helices, whereas the remaining 53 amino acids connected to DBD2 are disordered. Note the high similarity between the domains. (e) Structure of the E2F8 protein containing DBD1 (DBD^E2F, pink) and DBD2 (DBD^DP, blue) bound to a 15-base pair DNA fragment (green and yellow). Residues responsible for the motif recognition are presented as ball-and-stick models and coloured by atom (carbon: chain colour; nitrogen: blue; oxygen: red). The sequence of the DNA fragment is also shown.