YY1 is a sequence-specific DNA-binding transcription factor that has many important biological roles. It activates or represses many genes during cell growth and differentiation and is also required for the normal development of mammalian embryos. Previous studies have established that YY1 interacts with histone acetyltransferases p300 and CREB-binding protein (CBP) and histone deacetylase 1 (HDAC1), HDAC2, and HDAC3. Here, we present evidence that the activity of YY1 is regulated through acetylation by p300 and PCAF and through deacetylation by HDACs. YY1 was acetylated in two regions: both p300 and PCAF acetylated the central glycine-lysine-rich domain of residues 170 to 200, and PCAF also acetylated YY1 at the C-terminal DNA-binding zinc finger domain. Acetylation of the central region was required for the full transcriptional repressor activity of YY1 and targeted YY1 for active deacetylation by HDACs. However, the C-terminal region of YY1 could not be deacetylated. Rather, the acetylated C-terminal region interacted with HDACs, which resulted in stable HDAC activity associated with the YY1 protein. Finally, acetylation of the C-terminal zinc finger domain decreased the DNA-binding activity of YY1. Our findings suggest that in the natural context, YY1 activity is regulated through intricate mechanisms involving negative feedback loops, histone deacetylation, and recognition of the cognate DNA sequence affected by acetylation and deacetylation of the YY1 protein.YY1, also known as ␦, NF-E1, and UCRBP, is a multifunctional transcription factor. It binds, with its four C 2 H 2 zinc fingers, to a specific DNA sequence (CGCCATNTT) located in many different promoters and either activates or represses transcription (for comprehensive reviews, see references 57 and 65). YY1 regulates the expression of both cellular and viral genes, including those encoding c-Myc, c-Fos, p53, ␣-actin, gamma interferon, P5 of adeno-associated virus, E6 and E7 of human papillomavirus (HPV), and a number of other viral long terminal repeats. Many of these gene products have important consequences for cell growth and differentiation (reviewed in reference 57). YY1 is highly conserved among human, mouse, and Xenopus laevis cells, and a Drosophila melanogaster homologue of YY1 exists (6,14,20,47,49,58). Knockout studies show that deletion of YY1 results in periimplantation lethality in mice (13), further demonstrating the importance of YY1 in fundamental biological processes such as development.Various biochemical methods have been employed to dissect the functional domains of YY1 in order to understand how the activity of YY1 is regulated (1, 7, 8, 38-40, 58, 73). It can be summarized that YY1 contains two repression domains, one embedded within residues 170 to 200 and the other overlapping with the C-terminal zinc finger DNA-binding domain. YY1 might also contain an independent activation domain at the N terminus. This modular nature of YY1 supports the idea that YY1 is bifunctional, capable of both activating and repressing transcriptio...

Several human cDNAs encoding a histone deacetylase protein, HDAC3, have been isolated. Analysis of the predicted amino acid sequence of HDAC3 revealed an open reading frame of 428 amino acids with a predicted molecular mass of 49 kDa. The HDAC3 protein is 50% identical in DNA sequence and 53% identical in protein sequence compared with the previously cloned human HDAC1. Comparison of the HDAC3 sequence with human HDAC2 also yielded similar results, with 51% identity in DNA sequence and 52% identity in protein sequence. The expressed HDAC3 protein is functionally active because it possesses histone deacetylase activity, represses transcription when tethered to a promoter, and binds transcription factor YY1. Similar to HDAC1 and HDAC2, HDAC3 is ubiquitously expressed in many different cell types.The organization of chromatin structure is a fundamental and significant component of transcriptional regulation in all eukaryotic cells. Transcriptionally active or repressed chromatin is determined, at least in part, by the modification of histones. For example, hyperacetylation of histones generally leads to an increase in transcription, whereas hypoacetylation of histones appears to have the opposite effect (reviewed in Refs. 1-4). Nuclear histone acetyltransferases such as transcription factors GCN5, PCAF, p300/CBP, and TAF II 230/250 have been identified from different organisms (5-9).Several yeast and mammalian histone deacetylases have been identified, and their corresponding genes have been cloned (10 -12). In yeast, the HDA1 protein, which shares sequence similarity to RPD3, is a subunit of a large histone deacetylase complex HDA. RPD3 is also associated with another yeast histone deacetylase complex HDB. Using a trapoxin (an inhibitor of histone deacetylase) affinity matrix, Taunton et al. (10) purified and cloned a human 55-kDa protein related to the yeast protein RPD3. Immunoprecipitation of this 55-kDa protein, HDAC1 (also called HD1), showed that it contains histone deacetylase activity. A second human histone deacetylase protein, HDAC2, with high homology to yeast RPD3 was identified based on a yeast two-hybrid trap experiment with the YY1 transcription factor as a bait (11). YY1 negatively regulates transcription by tethering HDAC2 to DNA as a corepressor. Both HDAC1 and HDAC2 exist in a complex with the corepressor mSIN3 and mediate Mad transcriptional repression (13-15). In addition, HDAC1 and HDAC2 are essential components of two thyroid hormone receptor corepressors, N-CoR and SMRT (16 -18). HDAC1 is also an important factor that represses transactivation by progesterone receptor (19).The yeast RPD3 protein was originally identified in genetic screens for transcriptional repressors (20). Besides human and mouse, highly homologous yeast RPD3 sequences have been identified in Drosophila (21), Caenorhabditis elegans (X78454 and 1176665), and Xenopus laevis (gi:576995). Currently, it has not yet been established whether the C. elegans or X. laevis RPD3-related proteins have histone deacetylase activities o...

The metastasis-associated protein MTA1 has been shown to express differentially to high levels in metastatic cells. MTA2, which is homologous to MTA1, is a component of the NuRD ATP-dependent chromatin remodeling and histone deacetylase complex. Here we report evidence that although both human MTA1 and MTA2 repress transcription specifically, are located in the nucleus, and contain associated histone deacetylase activity, they exist in two biochemically distinct protein complexes and may perform different functions pertaining to tumor metastasis. Specifically, both MTA1 and MTA2 complexes exert histone deacetylase activity. However, the MTA1 complex contained HDAC1/2, RbAp46/48, and MBD3, but not Sin3 or Mi2, two important components of the MTA2 complex. Moreover, the MTA2 complex is similar to the HDAC1 complex, suggesting a housekeeping role of the MTA2 complex. The MTA1 complex could be further separated, resulting in a core MTA1-HDAC complex, showing that the histone deacetylase activity and transcriptional repression activity were integral properties of the MTA1 complex. Finally, MTA1, unlike MTA2, did not interact with the pleotropic transcription factor YY1 or the immunophilin FKBP25. We suggest that MTA1 associates with a different set of transcription factors from MTA2 and that this property may contribute to the metastatic potential of cells overexpressing MTA1. We also report the finding of human MTA3, which is highly homologous to both MTA1 and MTA2. However, MTA3 does not repress transcription to a significant level and appears to have a diffused pattern of subcellular localization, suggesting a biological role distinct from that of the other two MTA proteins.Metastasis represents one of the fundamental differences between benign and malignant tumors and poses a major obstacle in effective cancer treatment. The metastasis-associated gene 1 (MTA1) is closely associated with cancer metastasis. The rat mta1 gene was first identified using differential cDNA library screening techniques in a mammary adenocarcinoma metastatic system (1-3). The expression levels of MTA1 are elevated in human metastatic breast cell lines (2) and metastatic cancer tissues, such as breast, colorectal, gastric, and esophageal carcinomas (2, 4, 5). Overexpression of MTA1 correlates with enhancement of the ability of human breast cancer cells to invade and to grow in an anchorage-independent manner (6). In patients, colorectal and gastric carcinomas overexpressing MTA1 show deeper invasion and higher rates of penetration into lymph nodes (4). In culture, administration of antisense phosphorothioate oligonucleotides specific for MTA1 inhibits the rapid growth of human breast cancer cells that express high levels of MTA1 compared with normal breast epithelial cells (7).Although evidence shows that MTA1 is closely linked to cancer metastasis, it was unclear how MTA1 is involved in the metastatic process. Genetic studies in Caenorhabditis elegans suggest that MTA1 may function in embryonic patterning, determination of cell polarity,...