Thanatos-associated protein 7 associates with template activating factor-Ibeta and inhibits histone acetylation to repress transcription.
The posttranslational modifications of histones on chromatin or a lack thereof is critical in transcriptional regulation. Emerging studies indicate a role for histone-binding proteins in transcriptional activation and repression. We have previously identified template-activating factor-Ibeta (TAF-Ibeta, also called PHAPII, SET, and I(2)(pp2A)) as a component of a cellular complex called inhibitor of acetyltransferases (INHAT) that masks histone acetylation in vitro and blocks histone acetyltransferase (HAT)-dependent transcription in living cells. TAF-Ibeta has also been shown to associate with transcription factors, including nuclear receptors, to regulate their activities. To identify novel interactors of TAF-Ibeta, we employed a yeast two-hybrid screen and identified a previously uncharacterized human protein called thanatos-associated protein-7 (THAP7), a member of a large family of THAP domain-containing putative DNA-binding proteins. In this study we demonstrate that THAP7 associates with TAF-Ibeta in vitro and map their association domains to a C-terminal predicted coiled-coil motif on THAP7 and the central region of TAF-Ibeta. Similarly, stably transfected THAP7 associates with endogenous TAF-Ibeta in intact cells. Like TAF-Ibeta, THAP7 associates with histone H3 and histone H4 and inhibits histone acetylation. The histone-interacting domain of THAP7 is sufficient for this activity in vitro. Promoter-targeted THAP7 can also recruit TAF-Ibeta and silencing mediator of retinoid and thyroid receptors/nuclear hormone receptor corepressor (NCoR) proteins to promoters, and knockdown of TAF-Ibeta by small interfering RNA relieves THAP7-mediated repression, indicating that, like nuclear hormone receptors, THAP7 may represent a novel class of transcription factor that uses TAF-Ibeta as a corepressor to maintain histones in a hypoacetylated, repressed state.
Macfarlan
Todd
T
Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, USA.
Parker
J Brandon
JB
Nagata
Kyosuke
K
Chakravarti
Debabrata
D
D000107:Acetylation; D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins; D015536:Down-Regulation; D005786:Gene Expression Regulation; D056488:Histone Chaperones; D006657:Histones / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D025941:Protein Interaction Mapping; D034741:RNA, Small Interfering / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D020798:Two-Hybrid System Techniques
D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D056488:Histone Chaperones; D006657:Histones; D034741:RNA, Small Interfering; D012097:Repressor Proteins; C513473:SET protein, human; C498974:THAP7 protein, human; D014157:Transcription Factors