Figure 4.

hbrm activation domain shows homology to the activation domain of E2F1 and E1A 12S protein. (A) Alignment of amino acids 1,206–1,304 of the hbrm protein with the Ad12 E1A N terminus (amino acids 8–119) and the E2F1 activation domain (amino acids 373–437). Residues involved in RB and p300 binding in E1A and E2F1 are indicated. (B) RB binds and represses an activation domain in hbrm. C33A cells were transfected with 2 μg of G5E1B-CAT, 0.5 μg of GAL4 DNA binding domain, or GAL4-hbrm 1206–1304 fusion protein expression vectors and 0.5 μg of RB expression vectors as indicated. The activity of the promoter in the absence of hbrm and RB is normalized to a value of 1. Result of a typical experiment is shown.