Figure 5.

Activated Transcription Driven by a Single Type Activation Domain Is Sensitive to TBP C-Terminal Stirrup Mutations in Vivo.

Transcription of the Gal4–GUS reporter (Figure 3A, construct 5) was activated by coexpression with Gal4 DNA binding domain activator fusions in transient assays using maize cells. The effect of TBP C-terminal stirrup mutations on activated transcription was monitored by coexpression of TBP mutants with each Gal4 DNA binding domain activator as indicated. Three types of activation domain were tested as Gal4 DNA binding domain fusion proteins: (A) ftzQ; (B) Gal4; and (C) VP16. The null effector (Figure 3B, construct 9) used in bar 1 was included to show activity of endogenous TBP. Bars 2 to 6 represent expression of wild-type and mutant AtTBP, as indicated. Activity, given as a ratio of GUS/LUC units, is averaged from triplicate experiments. Standard errors are indicated. wt, wild type.