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Abstract
The SAGA histone acetyltransferase and TFIID complexes play key roles in eukaryotic transcription. Using hierarchical cluster analysis of mass spectrometry data to identify proteins that copurify with components of the budding yeast TFIID transcription complex, we discovered that an uncharacterized protein corresponding to the YPL047W open reading frame significantly associated with shared components of the TFIID and SAGA complexes. Using mass spectrometry and biochemical assays, we show that YPL047W (SGF11, 11-kDa SAGA-associated factor) is an integral subunit of SAGA. However, SGF11 does not appear to play a role in SAGA-mediated histone acetylation. DNA microarray analysis showed that SGF11 mediates transcription of a subset of SAGA-dependent genes, as well as SAGA-independent genes. SAGA purified from a sgf11Δ deletion strain has reduced amounts of Ubp8p, and a ubp8Δ deletion strain shows changes in transcription similar to those seen with the sgf11Δ deletion strain. Together, these data show that Sgf11p is a novel component of the yeast SAGA complex and that SGF11 regulates transcription of a subset of SAGA-regulated genes. Our data suggest that the role of SGF11 in transcription is independent of SAGA's histone acetyltransferase activity but may involve Ubp8p recruitment to or stabilization in SAGA.
We are grateful to Tracey Fleischer, Vince Gerbasi, Elizabeth Link, and Jay Kirchner for experimental advice throughout this study or for discussions and comments during the preparation of the manuscript. We also thank Jay Kirchner for the SAGA antibodies. We thank Jerry Workman for the purified nucleosomes. Lastly, we thank all of the members of the Vanderbilt Microarray Shared Resource Center for their assistance with microarray protocols and data analysis.
This study was supported by an NIH grant ES11993 and NCI SPORE Lung Cancer Pilot Project Initiative awarded to A.J.L. (1 P50 CA90949). D.W.P was supported by NIH training grant T32-HL69765. C.M.W. and J.L.J. are supported by NIH grants GM64779 and HL68744. K.J.M. is supported by NIH grants ES11993, GM64779, NS43952, and GM68900. P.A.W. is supported by NIH grants ES11993 and GM52461. A.J.L. is supported by NIH grants ES11993, GM64779, HL68744, NS43952, and CA098131.