ADR1-MEDIATED TRANSCRIPTIONAL ACTIVATION REQUIRES THE PRESENCE OF AN INTACT TFIID COMPLEX

The yeast transcriptional activator ADR1, which is required for ADH2 a nd other genes' expression, contains four transactivation domains (TAD s). While previous studies have shown that these TADs act through GCN5 and ADA2, and presumably TFIIB, other factors are likely to be involv ed in ADR1 function. In this study, we addressed the question of wheth er TFIID is also required for ADR1 action. In vitro binding studies in dicated that TADI of ADR1 was able to retain TAF(II)90 from yeast extr acts and TADII could retain TBP and TAF(II)130/145. TADIV, however, wa s capable of retaining multiple TAF(II)s, suggesting that TADIV was bi nding TFIID from yeast whole-cell extracts. The ability of TADIV trunc ation derivatives to interact with TFIID correlated with their transcr iption activation potential in vivo. In addition, the ability of LexA- ADR1-TADIV to activate transcription in vivo was compromised by a muta tion in TAF(II)130/145. ADR1 was found to associate in vivo with TFIID in that immunoprecipitation of either TAF(II)90 or TBP from yeast who le-cell extracts specifically coimmunoprecipitated ADR1, Most importan tly, depletion of TAF(II)90 from yeast cells dramatically reduced ADH2 derepression. These results indicate that ADR1 physically associates with TFIID and that its ability to activate transcription requires an intact TFIID complex.