Jun dimerization protein-2 (JDP2) is a component of the AP-1 transcription factor that represses transactivation mediated by the Jun family of proteins. Here, we examine the functional mechanisms of JDP2 and show that it can inhibit p300-mediated acetylation of core histones in vitro and in vivo. Inhibition of histone acetylation requires the N-terminal 35 residues and the DNA-binding region of JDP2. In addition, we demonstrate that JDP2 has histone-chaperone activity in vitro. These results suggest that the sequence-specific DNA-binding protein JDP2 may control transcription via direct regulation of the modification of histones and the assembly of chromatin.
General transcription initiation factor IID (TFIID) plays a central and critical role in transcription initiation from both naked and chromatin templates. Although interaction between several DNAbinding proteins and TFIID were identified and well characterized, functional linkage between TFIID and chromatin factors has remained to be elucidated. Here we show the identification and characterization of human CIA͞hASF1 (identified previously as a histone chaperone) as an interactor of two tandem bromodomain modules of human (h)TAF II250͞CCG1, the largest subunit of TFIID. Although yeast (y)TAF II145, a homologue of hTAFII250͞CCG1 in Saccharomyces cerevisiae, lacks bromodomains, glutathione Stransferase pull-down and immunoprecipitation assays revealed that Asf1p (antisilencing function 1), the counterpart of CIA in S. cerevisiae, interacts with Bdf1p (bromodomain factor 1), which is reported to serve as the missing bromodomain in yTAFII145. Furthermore, yeast strain lacking the BDF1 gene shows the Spt phenotype that is shown also by the ASF1 gene disruptant, and a double-knockout strain of both genes shows synthetic lethality, indicating that ASF1 genetically interacts with bromodomains associated with yTFIID. We also found that Asf1p coprecipitates with yTFIID subunits from yeast whole-cell extract, and overexpression of yTFIID subunits suppress the Spt phenotype caused by gene disruption of the ASF1. This study describes the functional linkage between TFIID and a histone chaperone. Chromosomal DNA in eukaryotes is packaged into chromatin, and the nucleosome is the fundamental structural unit of chromatin (1). Nucleosomes act as general repressors of transcription by RNA polymerase II, which transcribes proteincoding genes in eukaryotic cells (2-4). Initiation of transcription by RNA polymerase II is a multistep reaction in which several general transcription initiation factors are involved (5). Transcription initiation factor IID (TFIID) is the only general transcription initiation factor that specifically binds the TATA box that is found within the promoter of many mRNA-encoding genes and required for specific transcription initiation both in vivo and in vitro. Therefore it is suggested that binding of TFIID to the promoter is a crucial step for eukaryotic transcriptional regulation (6-8). To date, numerous functional interactions between TFIID and DNA binding activators͞repressors have been characterized (7-10). Functional interactions between TFIID and chromatin factors have remained to be elucidated, although they have been anticipated from studies showing that TFIID is not capable of binding to preassembled nucleosomes in vitro (11). Recently it was reported that histone acetyltransferase (HAT)-containing complexes and nucleosome remodeling factors affect the binding of TFIID to nucleosomal DNA templates (12,13).Biochemical studies have demonstrated that TFIID is a multisubunit complex comprised of TBP, the TATA box-binding protein, and several TBP-associated factors (TAF II s; refs. 14-16). TAF II 250͞cell ...
Background: Although no potential homologues of multicellular apoptotic genes (e.g. Bax, Bak, Bcl-2, caspases and p53) have been identified in a unicellular eukaryote, previous reports contain several implications of the apoptotic behaviour of yeasts (i.e. Saccharomyces cerevisiae and Schizosaccharomyces pombe). Therefore, whether or not yeast undergoes apoptosis has been a topic of some debate. hCCG1, which is the largest subunit of TFIID and a histone acetyltransferase, appears to be involved in the regulation of apoptosis. The factor hCIA interacts with hCCG1 and functions as a histone chaperone in mammalian cells; its homologue in yeast is Asf1p/Cia1p. Therefore, we anticipated that a yeast mutant in Asf1p/Cia1p would be a valuable tool for studying apoptosis in yeast.
Background : CIA, an interactor of the CCG1 histone acetyltransferase subunit of TFIID, was identified as a human histone chaperone. The Saccharomyces cerevisiae orthologue ASF1 , when it was over-expressed, was reported to cause de-repression of silent loci; however, the involvement of Asf1p in the alteration of nucleosomal structures remained unknown. Curiously, there is a polyanionic stretch, a structural motif characteristic of histone chaperones, in S. cerevisiae Asf1p, but not in human CIA. We investigated how CIA/Asf1p utilizes its domain(s) for the alteration of nucleosomal structure.
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