FIG. 6.

dTGIFs contain acidic activation domains. (A) The domains of dTGIFa are shown schematically above. The letter A represents the acidic region. A series of deletion mutants of dTGIFa fused to the GBD were created and assayed for expression levels by Western blotting with an antibody specific for the GBD. The specific bands are indicated by stars to the left of each lane. Lane numbers 1 to 12 refer to the numbers to the left of the schematic representation of the GBD-dTGIFa deletion series shown above. Amino acids contained in the fusion are shown to the right. The positions of molecular mass markers (in kilodaltons) are shown. A smaller series of GBD-dTGIFb deletions are shown schematically below. (B) The GBD-dTGIFa deletion series was cotransfected into L17 cells with the (Gal)₅TATA-luc reporter. Luciferase activity (mean ± standard deviation of triplicate transfections) is shown, together with that from cells expressing the GBD alone or without any GBD fusion. (C) A subset of GBD-dTGIFa fusions were coexpressed with the (Gal)₅-SV40 luciferase reporter to determine whether any of the nonactivating fusions could repress the activity of a promoter with a high basal activity. Luciferase activity was assayed, and the results are presented as in panel B. A series of GBD-dTGIFb deletions were cotransfected with the (Gal)₅TATA-luc reporter (D) or the (Gal)₅-SV40 luciferase reporter (E), and luciferase activity was assayed. The results are presented as described for panel B.