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Xiang-Jiao Yang

Publications and source records attributed to Xiang-Jiao Yang.

At least 19 recordsLinked to original sources
PubMed2006

Histone deacetylase 3 interacts with and deacetylates myocyte enhancer factor 2.

The myocyte enhancer factor 2 (MEF2) family of transcription factors is not only important for controlling gene expression in normal cellular programs, like muscle differentiation, T-cell apoptosis, neuronal survival, and synaptic differentiation, but has also been linked to cardiac hypertrophy and other pathological conditions. Lysine acetylation has been shown to modulate MEF2 function, but it is not so clear which deacetylase(s) is involved. We report here that treatment of HEK293 cells with trichostatin A or nicotinamide upregulated MEF2D acetylation, suggesting that different deacetylases catalyze the deacetylation. Related to the trichostatin A sensitivity, histone deacetylase 4 (HDAC4) and HDAC5, two known partners of MEF2, exhibited little deacetylase activity towards MEF2D. In contrast, HDAC3 efficiently deacetylated MEF2D in vitro and in vivo. This was specific, since HDAC1, HDAC2, and HDAC8 failed to do so. While HDAC4, HDAC5, HDAC7, and HDAC9 are known to recognize primarily the MEF2-specific domain, we found that HDAC3 interacts directly with the MADS box. In addition, HDAC3 associated with the acetyltransferases p300 and p300/CBP-associated factor (PCAF) to reverse autoacetylation. Furthermore, the nuclear receptor corepressor SMRT (silencing mediator of retinoid acid and thyroid hormone receptor) stimulated the deacetylase activity of HDAC3 towards MEF2 and PCAF. Supporting the physical interaction and deacetylase activity, HDAC3 repressed MEF2-dependent transcription and inhibited myogenesis. These results reveal an unexpected role for HDAC3 and suggest a novel pathway through which MEF2 activity is controlled in vivo.

Acetylation↗
PubMed2006

A recurrent phospho-sumoyl switch in transcriptional repression and beyond.

How multisite posttranslational modification coordinates dynamic regulation of protein function is an issue fundamental to many biological processes. Related to this, a composite sequence motif has recently been identified that couples phosphorylation, sumoylation, and perhaps also deacetylation to control transcriptional repression in stress response, mitogen and nuclear hormone signaling, myogenesis, and neuronal differentiation. This motif is present in many proteins, integrates cellular signals from diverse pathways, and serves as a valuable signature for in silico identification of proteins regulated by adjacent phosphorylation and sumoylation.

Acetylation↗
PubMed2006

A histone deacetylation-dependent mechanism for transcriptional repression of the gap junction gene cx43 in prostate cancer cells.

BACKGROUND: The connexin 43 gene (cx43, GJA1) mediates gap junctional intercellular communication (GJIC), which regulates tissue homeostasis. cx43 is frequently downregulated in prostate cancer. We investigated the role of a histone deacetylase (HDAC)-dependent mechanism in the transcriptional repression of cx43 in a panel of prostate cancer cells. METHODS: The impact of Trichostatin A (TSA), an inhibitor of HDAC, on exogenous and endogenous cx43 gene transcription was examined by the luciferase assay, Northern blot, nuclear run-on, Western blot, and chromatin immunoprecipitation assays. RESULTS: Trichostatin A induces transcription of cx43 gene and GJIC. The co-activator p300/CBP synergizes with TSA for cx43 promoter activation. We identified a promoter region where cooperation between Ap1 and Sp1 elements was essential for TSA-induced cx43 transcription. TSA increased the level of hyperacetylated histones bound to cx43 promoter. CONCLUSION: Our results highlight the potential utility of inhibitors of HDAC to restore cx43 gene expression in prostate cancer.

Acetylation↗
PubMed2006

ING tumor suppressor proteins are critical regulators of chromatin acetylation required for genome expression and perpetuation.

Members of the ING family of tumor suppressors regulate cell cycle progression, apoptosis, and DNA repair as important cofactors of p53. ING1 and ING3 are stable components of the mSin3A HDAC and Tip60/NuA4 HAT complexes, respectively. We now report the purification of the three remaining human ING proteins. While ING2 is in an HDAC complex similar to ING1, ING4 associates with the HBO1 HAT required for normal progression through S phase and the majority of histone H4 acetylation in vivo. ING5 fractionates with two distinct complexes containing HBO1 or nucleosomal H3-specific MOZ/MORF HATs. These ING5 HAT complexes interact with the MCM helicase and are essential for DNA replication to occur during S phase. Our data also indicate that ING subunits are crucial for acetylation of chromatin substrates. Since INGs, HBO1, and MOZ/MORF contribute to oncogenic transformation, the multisubunit assemblies characterized here underscore the critical role of epigenetic regulation in cancer development.

Acetylation↗
PubMed2006

Substrate and functional diversity of lysine acetylation revealed by a proteomics survey.

Acetylation of proteins on lysine residues is a dynamic posttranslational modification that is known to play a key role in regulating transcription and other DNA-dependent nuclear processes. However, the extent of this modification in diverse cellular proteins remains largely unknown, presenting a major bottleneck for lysine-acetylation biology. Here we report the first proteomic survey of this modification, identifying 388 acetylation sites in 195 proteins among proteins derived from HeLa cells and mouse liver mitochondria. In addition to regulators of chromatin-based cellular processes, nonnuclear localized proteins with diverse functions were identified. Most strikingly, acetyllysine was found in more than 20% of mitochondrial proteins, including many longevity regulators and metabolism enzymes. Our study reveals previously unappreciated roles for lysine acetylation in the regulation of diverse cellular pathways outside of the nucleus. The combined data sets offer a rich source for further characterization of the contribution of this modification to cellular physiology and human diseases.

Acetylation↗
PubMed2005

Control of MEF2 transcriptional activity by coordinated phosphorylation and sumoylation.

A eukaryotic protein is often subject to regulation by multiple modifications like phosphorylation, acetylation, ubiquitination, and sumoylation. How these modifications are coordinated in vivo is an important issue that is poorly understood but is relevant to many biological processes. We recently showed that human MEF2D (myocyte enhancer factor 2D) is sumoylated on Lys-439. Adjacent to the sumoylation motif is Ser-444, which like Lys-439 is highly conserved among MEF2 proteins from diverse species. Here we present [corrected] several lines of evidence to demonstrate that Ser-444 of MEF2D is required for sumoylation of Lys-439. Histone deacetylase 4 (HDAC4) stimulated this modification by acting through Ser-444. In addition, phosphorylation of Ser-444 by Cdk5, a cyclin-dependent kinase known to inhibit MEF2 transcriptional activity, stimulated sumoylation. Opposing the actions of HDAC4 and Cdk5, calcineurin (also known as protein phosphatase 2B) dephosphorylated Ser-444 and inhibited sumoylation of Lys-439. This phosphatase, however, exerted minimal effects on the phosphorylation catalyzed by ERK5, an extracellular signal-regulated kinase known to activate MEF2D. These results identify [corrected] an essential role for Ser-444 in MEF2D sumoylation and reveal [corrected] a novel mechanism by which calcineurin selectively "edits" phosphorylation at different sites, thereby reiterating that interplay between different modifications represents a general mechanism for coordinated regulation of eukaryotic protein functions in vivo.

Amino Acid Sequence↗
PubMed2005

Identification of the ankyrin repeat proteins ANKRA and RFXANK as novel partners of class IIa histone deacetylases.

Eighteen human histone deacetylases (HDACs) have been identified, and according to their sequence similarity to yeast homologs, these enzymes are grouped into distinct classes. Within class II, HDAC4, HDAC5, HDAC7, and HDAC9 share similar domain organization both within the N-terminal extension and the C-terminal catalytic domain, thus forming a subclass known as class IIa. These HDACs function as signal-responsive transcriptional corepressors. To gain further insight into their function and regulation, we utilized an N-terminal fragment of HDAC4 as bait in yeast two-hybrid screens, which uncovered myocyte enhancer factor 2C, 14-3-3zeta, and ankyrin repeat family A protein (ANKRA). ANKRA is a poorly characterized protein with an ankyrin repeat domain similar to RFXANK, a subunit of the trimeric transcription factor RFX. Mutations on genes of the RFX subunits and the coactivator CIITA are responsible for the bare lymphocyte syndrome, an immunodeficiency disorder attributed to the lack of major histocompatibility complex class II (MHCII) antigens. Through its ankyrin repeat domain, RFXANK interacted with HDAC4. Two RFXANK-binding sites were found on HDAC4 with one located within residues 118-279 and another within residues 448-666. Interestingly, this deacetylase also interacted with CIITA. Consistent with the physical interaction with RFXANK and CIITA, HDAC4 and homologs repressed MHCII expression. These results identify ANKRA, RFXANK, and CIITA as novel targets of class IIa HDACs and suggest that these deacetylases play a role in regulating MHCII expression.

14-3-3 Proteins↗
PubMed2005

Multisite protein modification and intramolecular signaling.

Post-translational modification is a major mechanism by which protein function is regulated in eukaryotes. Instead of single-site action, many proteins such as histones, p53, RNA polymerase II, tubulin, Cdc25C and tyrosine kinases are modified at multiple sites by modifications like phosphorylation, acetylation, methylation, ubiquitination, sumoylation and citrullination. Multisite modification on a protein constitutes a complex regulatory program that resembles a dynamic 'molecular barcode' and transduces molecular information to and from signaling pathways. This program imparts effects through 'loss-of-function' and 'gain-of-function' mechanisms. Among the latter, covalent modifications specifically recruit a diverse array of modules, including the SH2 domain, 14-3-3, WW domain, Polo box, BRCT repeat, bromodomain, chromodomain, Tudor domain and motifs binding to ubiquitin and other protein modifiers. Such recruitments are often modulated by modifications occurred at neighboring and distant sites. Multisite modification thus coordinates intermolecular and intramolecular signaling for the qualitative and quantitative control of protein function in vivo.

Acetylation↗
PubMed2005

Association with class IIa histone deacetylases upregulates the sumoylation of MEF2 transcription factors.

The myocyte enhancer factor-2 (MEF2) family of transcription factors plays an important role in regulating cellular programs like muscle differentiation, neuronal survival, and T-cell apoptosis. Multisite phosphorylation is known to control the transcriptional activity of MEF2 proteins, but it is unclear whether other modifications are involved. Here, we report that human MEF2D, as well as MEF2C, is modified by SUMO2 and SUMO3 at a motif highly conserved among MEF2 proteins from diverse organisms. This motif is located within the C-terminal transcriptional activation domain, and its sumoylation inhibits transcription. As a transcriptional corepressor of MEF2, histone deacetylase 4 (HDAC4) potentiates sumoylation. This potentiation is dependent on the N-terminal region but not the C-terminal deacetylase domain of HDAC4 and is inhibited by the sumoylation of HDAC4 itself. Moreover, HDAC5, HDAC7, and an HDAC9 isoform also stimulate sumoylation of MEF2. Opposing the action of class IIa deacetylases, the SUMO protease SENP3 reverses the sumoylation to augment the transcriptional and myogenic activities of MEF2. Similarly, the calcium/calmodulin-dependent kinases [corrected] and extracellular signal-regulated kinase 5 signaling pathways negatively regulate the sumoylation. These results thus identify sumoylation as a novel regulatory mechanism for MEF2 and suggest that this modification interplays with phosphorylation to promote intramolecular signaling for coordinated regulation in vivo.

Amino Acid Motifs↗
PubMed2004

Role of the tetradecapeptide repeat domain of human histone deacetylase 6 in cytoplasmic retention.

Histone deacetylase 6 (HDAC6) contains tandem catalytic domains and a ubiquitin-binding zinc finger and displays deacetylase activity toward acetylated microtubules. Here we show that unlike its orthologs from Caenorhabditis elegans, Drosophila, and mouse, human HDAC6 possesses a tetradecapeptide repeat domain located between the second deacetylase domain and the C-terminal ubiquitin-binding motif. Related to this structural difference, the cytoplasmic localization of human, but not murine, HDAC6 is resistant to treatment with leptomycin B (LMB). Although it is dispensable for the deacetylase and ubiquitin binding activities of human HDAC6, the tetradecapeptide repeat domain displays acetyl-microtubule targeting ability. Moreover, it forms a unique structure and is required for the LMB-resistant cytoplasmic localization of human HDAC6. Besides the tetradecapeptide repeat domain, human HDAC6 possesses two LMB-sensitive nuclear export signals and a nuclear localization signal. These results thus indicate that the cytoplasmic localization for murine and human HDAC6 proteins is differentially regulated and suggest that the tetradecapeptide repeat domain serves as an important sequence element to stably retain human HDAC6 in the cytoplasm.

Active Transport, Cell Nucleus↗
PubMed2004

Caspase-mediated specific cleavage of human histone deacetylase 4.

Histone deacetylase 4 (HDAC4) is a class II HDAC implicated in controlling gene expression important for diverse cellular functions, but little is known about how its expression and stability are regulated. We report here that this deacetylase is unusually unstable, with a half-life of less than 8 h. Consistent with the instability of HDAC4 protein, its mRNA was also highly unstable (with a half-life of less than 4 h). The degradation of HDAC4 could be accelerated by exposure of cells to ultraviolet irradiation. HDAC4 degradation was not dependent on proteasome or CRM1-mediated export activity but instead was caspase-dependent and was detectable in diverse human cancer lines. Of two potential caspase consensus motifs in HDAC4, both lying within a region containing proline-, glutamic acid-, serine-, and threonine-rich (PEST) sequences, we identified, by site-directed mutagenesis, Asp-289 as the prime cleavage site. Notably, this residue is not conserved among other class IIa members, HDAC5, -7, and -9. Finally, the induced expression of caspase-cleavable HDAC4 led to markedly increased apoptosis. These results therefore unexpectedly link the regulation of HDAC4 protein stability to caspases, enzymes that are important for controlling cell death and differentiation.

Amino Acid Motifs↗
PubMed2004

Akt binds prohibitin 2 and relieves its repression of MyoD and muscle differentiation.

In a yeast two-hybrid screen using the full-length Akt as bait, we found that prohibitin 2 (PHB2) specifically interacts with Akt. The C terminus of Akt (amino acids 413-480) and a central region of PHB2 (amino acids 120-232) are responsible for their mutual interaction. PHB2 acts as a transcriptional repressor in cells. PHB2 interacts with both MyoD and MEF2, and represses both MyoD- and MEF2-dependent gene transcription. Furthermore, binding of PHB2 to both MyoD and MEF2 significantly decreases upon myogenic differentiation. When stably expressed in C2C12 myogenic cells, PHB2 inhibits myogenin induction and phenotypic muscle differentiation. PHB2 was found to specifically recruit histone deacetylase 1, which is probably responsible for its repressive activity. Co-expression of Akt can partially reduce PHB2 binding to MyoD and relieve the repressive effect of PHB2 on myogenic reporters, which could be one of the mechanisms underlying Akt-mediated MyoD activation and accelerated muscle differentiation.

Animals↗
PubMed2004

The diverse superfamily of lysine acetyltransferases and their roles in leukemia and other diseases.

Acetylation of the epsilon-amino group of lysine residues, or N(epsilon)-lysine acetylation, is an important post-translational modification known to occur in histones, transcription factors and other proteins. Since 1995, dozens of proteins have been discovered to possess intrinsic lysine acetyltransferase activity. Although most of these enzymes were first identified as histone acetyltransferases and then tested for activities towards other proteins, acetyltransferases only modifying non-histone proteins have also been identified. Lysine acetyltransferases form different groups, three of which are Gcn5/PCAF, p300/CBP and MYST proteins. While members of the former two groups mainly function as transcriptional co-activators, emerging evidence suggests that MYST proteins, such as Esa1, Sas2, MOF, TIP60, MOZ and MORF, have diverse roles in various nuclear processes. Aberrant lysine acetylation has been implicated in oncogenesis. The genes for p300, CBP, MOZ and MORF are rearranged in recurrent leukemia-associated chromosomal abnormalities. Consistent with their roles in leukemogenesis, these acetyltransferases interact with Runx1 (or AML1), one of the most frequent targets of chromosomal translocations in leukemia. Therefore, the diverse superfamily of lysine acetyltransferases executes an acetylation program that is important for different cellular processes and perturbation of such a program may cause the development of cancer and other diseases.

Acetylation↗
PubMed2004

Lysine acetylation and the bromodomain: a new partnership for signaling.

Lysine acetylation has been shown to occur in many protein targets, including core histones, about 40 transcription factors and over 30 other proteins. This modification is reversible in vivo, with its specificity and level being largely controlled by signal-dependent association of substrates with acetyltransferases and deacetylases. Like other covalent modifications, lysine acetylation exerts its effects through "loss-of-function" and "gain-of-function" mechanisms. Among the latter, lysine acetylation generates specific docking sites for bromodomain proteins. For example, bromodomains of Gcn5, PCAF, TAF1 and CBP are able to recognize acetyllysine residues in histones, HIV Tat, p53, c-Myb or MyoD. In addition to the acetyllysine moiety, the flanking sequences also contribute to efficient recognition. The relationship between acetyllysine and bromodomains is reminiscent of the specific recognition of phosphorylated residues by phospho-specific binding modules such as SH2 domains and 14-3-3 proteins. Therefore, lysine acetylation forges a novel signaling partnership with bromodomains to govern the temporal and spatial regulation of protein functions in vivo.

Acetylation↗
PubMed2004

Corepressor recruitment by agonist-bound nuclear receptors.

Members of the nuclear receptor superfamily are ligand-regulated transcription factors that are composed of a series of conserved domains. These receptors are targets of a wide range of lipophilic signaling molecules that modulate many aspects of physiology and metabolism. Binding of cognate ligands to receptors induces a conformational change in the ligand binding domain (LBD) that creates a pocket for recruitment of coregulatory proteins, which are essential for ligand-dependent regulation of transcription. Several coregulatory proteins that interact with hormone-bound receptors contain characteristic helical LXXLL motifs, known as nuclear receptor (NR) boxes. Generally, ligand binding to receptors is associated with activation of transcription, and most of the NR box-containing proteins characterized to date are coactivators. However, a full understanding of the function of hormone-bound receptors must also incorporate their recruitment of corepressors. The recent identification of ligand-dependent corepressor (LCoR) is a case in point. LCoR contains a single NR box that mediates its hormone-dependent interaction with several nuclear receptors. It functions as a molecular scaffold that recruits several proteins that function in transcriptional repression. Remarkably, although the two proteins share only very limited homology, LCoR and another NR box-containing corepressor RIP140 recruit similar cofactors implicated in transcriptional repression, suggesting many parallels in their mechanisms of action. Corepressors such as LCoR and RIP140 may function in negative feedback loops to attenuate hormone-induced transactivation, act more transiently as part of a cycle of cofactors recruited to target promoters by ligand-bound receptors, or function in hormone-induced target gene repression.

Adaptor Proteins, Signal Transducing↗
PubMed2003

PCAF is a coactivator for p73-mediated transactivation.

The tumor suppressor p53-related p73 shares significant amino-acid sequence identity with p53. Like p53, p73 recognizes canonical p53 DNA-binding sites and activates p53-responsive target genes and induces apoptosis. Moreover, transcription coactivator p300/CBP binds to and coactivates with both p53 and p73 in stimulating the expression of their target genes. Here, we report that coactivator PCAF binds to p73. The N-terminal transactivation domain (TAD) and the conserved oligomerization domain (OD) of p73 are both required for its interaction with PCAF. Conversely, PCAF's HAT-domain is required for and both the N-terminal region and Bromo domain enhance binding of PCAF to p73. Significantly, PCAF stimulates p73-mediated transactivation, and binding of PCAF to p73 is necessary for p73's transactivation activity. PCAF-specific siRNA dramatically reduces p73-mediated transactivation. Stimulation of p73-mediated transactivation by PCAF requires the HAT domain of PCAF and the p53-binding site within the p21 promoter. In vivo, coexpression of wild-type, but not HAT-deficient PCAF with p73beta markedly increases p21 expression. Furthermore, cotransfection of PCAF and p73 leads to increased apoptosis and reduced colony formation. Collectively, these data suggest that p73 recruit PCAF to specific promoters to activate the transcription of p73 target genes.

Apoptosis↗
PubMed2003

Functional characterization of an amino-terminal region of HDAC4 that possesses MEF2 binding and transcriptional repressive activity.

Like the full-length histone deacetylase (HDAC) 4, its amino terminus (amino acids 1-208) without the carboxyl deacetylase domain is also known to effectively bind and repress myocyte enhancer factor 2 (MEF2). Within this repressive amino terminus, we further show that a stretch of 90 amino acids (119-208) displays MEF2 binding and repressive activity. The same region is also found to associate specifically with HDAC1 which is responsible for the repressive effect. The amino terminus of HDAC4 can associate with the DNA-bound MEF2 in vitro, suggesting that it does not repress MEF2 simply by disrupting the ability of MEF2 to bind DNA. In vivo, MEF2 induces nuclear translocation of both the full-length HDAC4 and HDAC4-(1-208), whereas the nuclear HDAC4 as well as HDAC4-(1-208) in turn specifically sequesters MEF2 to distinct nuclear bodies. In addition, we show that MyoD and HDAC4 functionally antagonize each other to regulate MEF2 activity. Combined with data from others, our data suggest that the full-length HDAC4 can repress MEF2 through multiple independent repressive domains.

Active Transport, Cell Nucleus↗