A Subset of TAFIIs Are Integral Components of the SAGA Complex Required for Nucleosome Acetylation and Transcriptional Stimulation

AbstractA number of transcriptional coactivator proteins have been identified as histone acetyltransferase (HAT) proteins, providing a direct molecular basis for the coupling of histone acetylation and transcriptional activation. The yeast Spt-Ada-Gcn5-acetyltransferase (SAGA) complex requires the coactivator protein Gcn5 for HAT activity. Identification of protein subunits by mass spectrometry and immunoblotting revealed that the TATA binding protein–associated factors (TAFIIs) TAFII90, -68/61, -60, -25/23, and -20/17 are integral components of this complex. In addition, TAFII68 was required for both SAGA-dependent nucleosomal HAT activity and transcriptional activation from chromatin templates in vitro. These results illustrate a role for certain TAFII proteins in the regulation of gene expression at the level of chromatin modification that is distinct from the TFIID complex and TAFII145