FIG. 1.

ts13 TAF_II250 mutant protein displays ts HAT activity in vitro. (A) Schematic diagram of human TAF_II250 protein. The positions of known functional domains are indicated. The homologous human amino acid residue mutated in ts13 cells (G716) maps to the putative HAT domain of TAF_II250, suggesting that this enzymatic activity is compromised in ts13 cells. Term, terminal; NLS, nuclear localization signal. WT and mutant TAF_II250 were purified from baculovirus-infected Sf9 extracts using immunoprecipitation techniques, run on SDS-polyacrylamide gels, and visualized by Coomassie blue staining to show purity. As a control, Sfa lysis buffer was subjected to immunoprecipitation. Positions of the immunoglobulin heavy (IgG_H) and light (IgG_L) chains are indicated. Positions of molecular weight standards (MW) are indicated in kilodaltons at the left. BSA, bovine serum albumin. (C) Purified TAF_II250 proteins described for panel B were added to liquid HAT assays containing purified calf thymus histones and [³H]acetyl coenzyme A and incubated at 25°C (six experiments with 5 ≤ n ≤ 10) or 37°C (eight experiments with 5 ≤ n ≤ 10). The amount of acetylated histones was measured by liquid scintillation.