Fig. 7. Dominant negative activity of HESX1(R160C) requires amino terminal repression domain. (A) Dominant negative activity of HESX1(R160C) in vitro. Recombinant HESX1(R160C) (50-200 nM) was mixed together with wild-type HESX1 protein (100 nM) and incubated with radiolabeled DNA containing a P3 binding site. The numbers above the lanes indicate the molar ratio of HESX1(R160C) or heat denatured (denoted by *) HESX1(R160C) to wild-type protein. (B) Dominant negative activity of HESX1 in vivo depends on the amino terminal repression domain. Increasing concentrations of wild-type HESX1-VP4 expression vector (20, 50, 150 and 400 ng) were co-transfected with the P3 luciferase reporter. Wild-type HESX1-VP4 expression vector was co-transfected with 400 ng of either HESX1(R160C)-VP4 or HESX1(R160C)(50-185)-VP4.