Fig. 3. Human TRIP-Br domains with homology to E2F-1 and MDM2. (A) Comparison of the domain structure and amino acid identity of the TRIP-Br proteins. The minimal region of TRIP-Br1 (aa 161–178) required for interaction with the PHD-bromodomain is indicated by brackets. P, proline-rich; S/A, serine/alanine-rich; S/T, serine/threonine-rich. (B) N-terminal sequences of the human TRIP-Br proteins are shown aligned with the cyclin A-binding domain of E2F-1. Boxed residues indicate amino acids that are similar between E2F-1 and at least one of the TRIP-Br proteins, and shaded boxes indicate residues that are identical between E2F-1 and at least one of the TRIP-Br proteins. (C) N-terminal sequences of the human TRIP-Br proteins are shown aligned with the heptad repeat region of E2F-1. Amino acids are boxed and shaded as in (B). Asterisks shown below indicate the heptad periodicity characteristic of E2F-1 and DP-1, which is also shared by the TRIP-Br proteins. Asterisks shown above indicate a novel heptad periodicity, which occurs only in the TRIP-Br proteins. (D) Amino acids in the putative heptad repeat regions of the human TRIP-Br proteins and E2F-1 are displayed in an α-helical wheel. Hydrophobic residues that occur in positions 1 and 4, corresponding to the two heptad periodicities shown in (C), are boxed. Charged residues are circled. (E) C-terminal sequences of the human TRIP-Br proteins are shown aligned with the MDM2 transactivation domain. Amino acids are boxed and shaded as in (B).