FIGURE 3 - uploaded by Kwang Il Nam
Content may be subject to copyright.
Epc1 and SRF synergistically induce muscle-specific genes. A , cotransfection of SRF and Epc1 synergistically induced skeletal ␣ -actin, MyoD, and myogenin proteins in C2C12 cells. B , quantification of protein amounts from three independent immunoblots. C , SRF and Epc1 elevated the transcript levels of skeletal ␣ -actin, muscle creatine kinase ( MCK ), myogenin, and MyoD , but not myf-6 in 10T1/2 cells. D , real-time PCR analysis for quantification of the transcript levels of skeletal ␣ -actin, MCK , myogenin , and MyoD from three independent sets of experiments. Error bars represent S.E.
Source publication
Skeletal muscle differentiation is well regulated by a series of transcription factors. We reported previously that enhancer
of polycomb1 (Epc1), a chromatin protein, can modulate skeletal muscle differentiation, although the mechanisms of this action
have yet to be defined. Here we report that Epc1 recruits both serum response factor (SRF) and p30...
Similar publications
The adaptation of the cellular network to functional changes, timing and patterning of gene expression is regulated by binding of transcription factors to gene regulatory elements, which in turn depends on co-occurring histone modifications. These two layers influence each other, enabling a further level of regulatory fine-tuning. We analyzed the i...
Significance
The inositol polyphosphate system is a major intracellular signaling modality. Inositol polyphosphate multikinase (IPMK) is essential for this system, converting inositol 1,4,5-trisphosphate (IP3) to IP4 and IP4 to IP5. IPMK also is a physiologic PI3-kinase. In a noncatalytic manner, IPMK stabilizes the mammalian target of rapamycin (m...
Citations
... The active repression of senescence pathways via the polycomb proteins is an important aspect of the maintenance of satellite cell quiescence and self-renewal with age [89]. The polycomb proteins catalyze the acetylation of H3K27 [90] by recruiting histone acetyltransferases such as p300, leading to the activation of gene expression [91]. In addition to this, polycomb proteins may also ubiquitinate histone 2A, making chromatin more accessible to gene expression. ...
Significant loss of muscle mass may occur in cachexia and sarcopenia, which are major causes of mortality and disability. Cachexia represents a complex multi-organ syndrome associated with cancer and chronic diseases. It is often characterized by body weight loss, inflammation, and muscle and adipose wasting. Progressive muscle loss is also a hallmark of healthy aging, which is emerging worldwide as a main demographic trend. A great challenge for the health care systems is the age-related decline in functionality which threatens the independence and quality of life of elderly people. This biological decline can also be associated with functional muscle loss, known as sarcopenia. Previous studies have shown that microRNAs (miRNAs) play pivotal roles in the development and progression of muscle wasting in both cachexia and sarcopenia. These small non-coding RNAs, often carried in extracellular vesicles, inhibit translation by targeting messenger RNAs, therefore representing potent epigenetic modulators. The molecular mechanisms behind cachexia and sarcopenia, including the expression of specific miRNAs, share common and distinctive trends. The aim of the present review is to compile recent evidence about shared and divergent epigenetic mechanisms, particularly focusing on miRNAs, between cachexia and sarcopenia to understand a facet in the underlying muscle wasting associated with these morbidities and disclose potential therapeutic interventions.
... Serum response factor (SRF) is critical for cell survival and differentiation 1,5,8,9 . SRF directly binds to the serum response element (SRE) in the promoter of its target genes [8][9][10] . ...
... Serum response factor (SRF) is critical for cell survival and differentiation 1,5,8,9 . SRF directly binds to the serum response element (SRE) in the promoter of its target genes [8][9][10] . Many of the biological activities of SRF, such as DNA binding, self-dimerization, and interaction with other transcription factors, take place at the conserved MADS (MCM1, agamous, deficiens)-box domain 11,12 . ...
... Many of the biological activities of SRF, such as DNA binding, self-dimerization, and interaction with other transcription factors, take place at the conserved MADS (MCM1, agamous, deficiens)-box domain 11,12 . In skeletal muscle cells, SRF functions as a transcription factor to induce SRF-dependent muscle-specific genes 8,9,13 . In addition to its role in DNA binding, the MADS-box recruits other transcription factors to form multicomponent regulatory complexes. ...
The demethylation of histone lysine residues, one of the most important modifications in transcriptional regulation, is associated with various physiological states. KDM2B is a demethylase of histones H3K4, H3K36, and H3K79 and is associated with the repression of transcription. Here, we present a novel mechanism by which KDM2B demethylates serum response factor (SRF) K165 to negatively regulate muscle differentiation, which is counteracted by the histone methyltransferase SET7. We show that KDM2B inhibited skeletal muscle differentiation by inhibiting the transcription of SRF-dependent genes. Both KDM2B and SET7 regulated the balance of SRF K165 methylation. SRF K165 methylation was required for the transcriptional activation of SRF and for the promoter occupancy of SRF-dependent genes. SET7 inhibitors blocked muscle cell differentiation. Taken together, these data indicate that SRF is a nonhistone target of KDM2B and that the methylation balance of SRF as maintained by KDM2B and SET7 plays an important role in muscle cell differentiation.
... Loss of TIP60 protein expression in mice results in embryonic death [2,3], whereas disruption of Epc1 is controversial, resulting in a viable or embryonic lethal phenotype under homozygous conditions depending on the deleted or disrupted exons [4,5]. EAF6 has been attributed to a critical function in genomic regulation [6,7], yet no mutant mouse model has been described. ...
The ING3 candidate tumour suppressor belongs to a family of histone modifying proteins involved in regulating cell proliferation, senescence, apoptosis, chromatin remodeling, and DNA repair. It is a stoichiometric member of the minimal NuA4 histone acetyl transferase (HAT) complex consisting of EAF6, EPC1, ING3, and TIP60. This complex is responsible for the transcription of an essential cascade of genes involved in embryonic development and in tumour suppression. ING3 has been linked to head and neck and hepatocellular cancers, although its status as a tumour suppressor has not been well established. Recent studies suggest a pro-metastasis role in prostate cancer progression. Here, we describe a transgenic mouse strain with insertional mutation of an UbC-mCherry expression cassette into the endogenous Ing3 locus, resulting in the disruption of ING3 protein expression. Homozygous mutants are embryonically lethal, display growth retardation, and severe developmental disorders. At embryonic day (E) 10.5, the last time point viable homozygous embryos were found, they were approximately half the size of heterozygous mice that develop normally. µCT analysis revealed a developmental defect in neural tube closure, resulting in the failure of formation of closed primary brain vesicles in homozygous mid-gestation embryos. This is consistent with high ING3 expression levels in the embryonic brains of heterozygous and wild type mice and its lack in homozygous mutant embryos that show a lack of ectodermal differentiation. Our data provide direct evidence that ING3 is an essential factor for normal embryonic development and that it plays a fundamental role in prenatal brain formation.
... EPC1 regulates skeletal muscle differentiation through interaction with HOP (Homeodomain Only Protein) and also recruits Serum Response Factor (SRF) and p300, in a manner that appears to be independent of NuA4/ TIP60. Indeed, TIP60 is undetectable in various muscle cell lines and tissues (Kee et al. 2007;Kim et al. 2009). The positive regulation of skeletal muscle differentiation by the EPC1-HOP interaction is opposed by an interaction between EPC1 and RFP, whereby RFP blocks the skeletal muscle differentiation that is induced by the collaboration of EPC1 and HOP (Kee et al. 2012). ...
... Although some studies have assigned domains required for interactions reported here (Table 2), a CRISPR-Cas9-based approach would facilitate a more comprehensive functional assignment for specific residues, and may correspondingly be used to test the significance of cancer-associated mutations. Along these lines, a recent study reported generation of a viable Epc1 −/− mouse (Dong et al. 2017), whereas previous studies demonstrated that homozygous deletion of Epc1 resulted in embryonic lethality (Kim et al. 2009). The specific Epc1 residues involved in the disruption might explain this apparent disparity in the necessity for EPC1 in mice. ...
... The specific Epc1 residues involved in the disruption might explain this apparent disparity in the necessity for EPC1 in mice. The viable Epc1 −/− mice were generated by disrupting exons 3-5 (Dong et al. 2017) thereby leaving the EPcA domain largely intact, whereas the non-viable homozygous null Epc1 knockout mice involved disruption within the first exon (Kim et al. 2009). These differing results underscore the importance of considering structure-function when assessing EPC. ...
Enhancer of Polycomb (EPC) was first identified for its contributions to development in Drosophila and was soon-thereafter purified as a subunit of the NuA4/TIP60 acetyltransferase complex. Since then, EPC has often been left in the shadows as an essential, yet non-catalytic subunit of NuA4/TIP60; however, its deep conservation and disease association make clear that it warrants additional attention. In fact, recent studies in yeast demonstrated that its Enhancer of Polycomb, Epl1, was just as important for gene expression and acetylation as is the catalytic subunit of NuA4. Despite its conservation, studies of EPC have often remained siloed between organisms. Here, our goal is to provide a cohesive view of the current state of the EPC literature as it stands among the major model organisms in which it has been studied. EPC is involved in multiple processes, beginning with its cardinal role in regulating global and targeted histone acetylation. EPC also frequently serves as an important interaction partner in these basic cellular functions, as well as in multicellular development, such as in hematopoiesis and skeletal muscle differentiation, and in human disease. Taken together, a unifying theme from these studies highlights EPC as a critical genomic regulator.
... Luciferase reporter assay, RNA isolation, quantitative realtime PCR, western blotting and immunoprecipitation analyses These procedures have been previously described. [21][22][23] The primer sequences for quantitative real-time PCR will be provided upon request. The real-time PCR amplification products were confirmed by sequencing. ...
... The chromatin immunoprecipitation assay was performed as previously described, 22 with slight modifications. Briefly, cells were treated with 1% formaldehyde (Sigma) for 10 min to induce crosslinking at room temperature and neutralized with 0.125 M glycine. ...
Sumoylation, the conjugation of a small ubiquitin-like modifier (SUMO) protein to a target, has diverse cellular effects. However, the functional roles of the SUMO modification during myogenesis have not been fully elucidated. Here, we report that basal sumoylation of histone deacetylase 1 (HDAC1) enhances the deacetylation of MyoD in undifferentiated myoblasts, whereas further sumoylation of HDAC1 contributes to switching its binding partners from MyoD to Rb to induce myocyte differentiation. Differentiation in C2C12 skeletal myoblasts induced new immunoblot bands above HDAC1 that were gradually enhanced during differentiation. Using SUMO inhibitors and sumoylation assays, we showed that the upper band was caused by sumoylation of HDAC1 during differentiation. Basal deacetylase activity was not altered in the SUMO modification-resistant mutant HDAC1 K444/476R (HDAC1 2R). Either differentiation or transfection of SUMO1 increased HDAC1 activity that was attenuated in HDAC1 2R. Furthermore, HDAC1 2R failed to deacetylate MyoD. Binding of HDAC1 to MyoD was attenuated by K444/476R. Binding of HDAC1 to MyoD was gradually reduced after 2 days of differentiation. Transfection of SUMO1 induced dissociation of HDAC1 from MyoD but potentiated its binding to Rb. SUMO1 transfection further attenuated HDAC1-induced inhibition of muscle creatine kinase luciferase activity that was reversed in HDAC1 2R. HDAC1 2R failed to inhibit myogenesis and muscle gene expression. In conclusion, HDAC1 sumoylation plays a dual role in MyoD signaling: enhancement of HDAC1 deacetylation of MyoD in the basally sumoylated state of undifferentiated myoblasts and dissociation of HDAC1 from MyoD during myogenesis.
... The maintenance of satellite cell quiescence and self-renewal with age has also been shown to depend on the active repression of senescence pathways via the polycomb proteins [168]. The polycomb proteins are methyltransferases that catalyze acetylation of H3K27 [175] via the recruitment of the histone acetyltransferases, such as p300, ultimately activating gene expression of muscle-specific genes [176]. Furthermore, polycomb proteins also ubquitinate histone 2A making chromatin more permissive to allow gene expression. ...
Early-life environmental encounters, particularly following altered nutrient availability, affect muscle size, strength, and metabolic characteristics into older age. Loss of muscle mass and function with age (sarcopenia) is associated with frailty, impaired health span, and reduced quality of life. As adult skeletal muscle fibers are postmitotic, growth, maintenance, repair, and regeneration are dependent on mitotically capable muscle stem cells, called satellite cells. These cells reduce in number and function in aged muscle. Understanding mechanisms that underpin such cellular adaptations with age and have the potential to reduce or delay them, is therefore important. Within the skeletal muscle aging field, epigenetics, relating to understanding environmental control of gene activity and expression which are not dependent on the genetic DNA code itself, is now emerging as an important modulator of muscle stem cell function. Early-life epigenetic modifications may underlie the skeletal muscle response to later life encounters of the same environmental stimulus, thus influencing muscle mass and function with advancing age. Epigenetic modifications to DNA, histones, and chromatin that contribute to impaired adult myogenesis and depletion of the stem cell pool into older age will therefore be highlighted and discussed. Further, a current opinion on the potential for the stable retention of epigenetic modifications, over time, in skeletal muscle tissue or satellite cells following an early-life anabolic or catabolic event and the potential impact on loss of skeletal muscle with age will be provided.
... Actin dynamics influence cellular behavior not only by regulating cytoskeletal organization but also by controlling gene expression. For example, in skeletal muscle differentiation, disassembly of actin filaments is required for the muscle-specific gene expression induced by serum response factor (SRF) [29][30][31][32]. G-actin binds to megakaryocytic acute leukemia (MAL; also known as MKL1/MRTF-A), a cofactor of SRF, and sequesters it from the nucleus, therefore, causing alterations in the equilibrium between actin polymerization and depolymerization perturb differentiation [33]. ...
Mechanical microenvironments, such as extracellular matrix stiffness and strain, have crucial roles in cancer progression. Cells sense their microenvironments with mechanosensing biomolecules, which is accompanied by the modulation of actin cytoskeleton structures, and the signals are subsequently transduced downstream as biochemical signals. The tumor suppressors p53 and retinoblastoma protein (Rb) are known to prevent cancer progression. The p53 and Rb signaling pathways are disrupted in many types of cancers. Here, we review recent findings about the roles of these tumor suppressors in the regulation of mechanosensing biomolecules and the actin cytoskeleton. We further discuss how dysfunction in the p53- and/or Rb-mediated mechanosignaling pathways is potentially involved in cancer progression. These pathways might provide good targets for developing anticancer therapies.
... Enhancer of polycomb 1 (EPC1) is an essential sub unit in the chromatin regulatory complex, NuA4. In mammalian biology, EPC1 is involved in regulation of skeletal muscle differentiation [29] and seems to have a critical role in leukemic hematopoiesis over and above regulation of oncogene CMyc. EPC1 prevented accu mulation of CMyc and acute myeloid leukemia cell apoptosis [30]. ...
Acetylation is a major modification that is required for gene regulation, genome maintenance and metabolism. A dysfunctional acetylation plays an important role in several diseases, including cancer. A group of enzymes-lysine acetyltransferases are responsible for this modification and act in regulation of transcription as cofactors and by acetylation of histones and other proteins. Tip60, a member of MYST family, is expressed ubiquitously and is the acetyltransferase catalytic subunit of human NuA4 complex. This HAT has a well-characterized involvement in many processes, such as cellular signaling, DNA damage repair, transcriptional and cellular cycle. Aberrant lysine acetyltransferase functions promote or suppress tumorigenesis in different cancers such as colon, breast and prostate tumors. Therefore, Tip60 might be a potential and important therapeutic target in the cancer treatment; new histone acetyl transferase inhibitors were identified and are more selective inhibitors of Tip60.
... In mammalian biology, most reports focused on the function of EPC1 regarding mouse skeletal muscle differentiation (72)(73)(74). EPC1 is required for initiating skeletal muscle differentiation and appears to induce relevant genes via the interaction with Homeodomain Only Protein (Hop), serum response factor (SRF), and/or RET finger protein (RFP) in mice (69,(74)(75). Apart from this, there are only a few hints linking EPC1 to cancer. ...
... In mammalian biology, most reports focused on the function of EPC1 regarding mouse skeletal muscle differentiation (72)(73)(74). EPC1 is required for initiating skeletal muscle differentiation and appears to induce relevant genes via the interaction with Homeodomain Only Protein (Hop), serum response factor (SRF), and/or RET finger protein (RFP) in mice (69,(74)(75). Apart from this, there are only a few hints linking EPC1 to cancer. The gene is mapped to human chromosome 10p11, a genomic region frequently rearranged in various human tumors (76,77). ...
Transcription factor E2F1 is a key regulator of cell proliferation and apoptosis. Recently, it has been shown that aberrant E2F1 expression often detectable in advanced cancers contributes essentially to cancer cell propagation and characterizes the aggressive potential of a tumor. Conceptually, this requires a subset of malignant cells capable of evading apoptotic death through anticancer drugs. The molecular mechanism by which the pro-apoptotic activity of E2F1 is antagonized is widely unclear. Here we report a novel function for EPC1 (enhancer of polycomb homolog 1) in DNA damage protection. Depletion of EPC1 potentiates E2F1-mediated apoptosis in response to genotoxic treatment and abolishes tumor cell motility. We found that E2F1 directly binds to the EPC1 promoter and EPC1 vice versa physically interacts with bifunctional E2F1 to modulate its transcriptional activity in a target gene-specific manner. Remarkably, nuclear-colocalized EPC1 activates E2F1 to upregulate the expression of anti-apoptotic survival genes such as BCL-2 or Survivin/BIRC5 and inhibits death-inducing targets. The uncovered cooperativity between EPC1 and E2F1 triggers a metastasis-related gene signature in advanced cancers that predicts poor patient survival. These findings unveil a novel oncogenic function of EPC1 for inducing the switch into tumor progression-relevant gene expression that may help to set novel therapies.
... In addition to direct deacetylation of p53, Sirt1 can also act indirectly, through deacetylation of the histone acetyltransferase kat2b/p300, with comparable outcomes (the more Sirt1, the less active p53) [50]. Interestingly, Enhancer of PolyComb homolog 1 (EPC1), approximately affected by mutation in 3% of PDAC cases [6]), and a component of the NuA4 histone acetyltransferase (HAT) complex, binds directly to p300 [51]. Additionally, acetylation of Epc1 was reported to be significantly higher on Sirt1 knockout cells [25], suggesting that Epc1 could be a direct target of Sirt1. ...
Sirtuin 1 is a protein deacetylase that regulates a large number of proteins often functionally implicated in tumor development and progression. Its pleiotropic function has turned SIRT1 into an attractive chemotherapeutic target, underscored by very promising preclinical results with SIRT1 inhibitors in the treatment of chronic myeloid leukemia. Here, we revisit the studies on SIRT1 as an emerging target for therapy in pancreatic cancer, a tumor with dismal outcomes for which currently few therapeutic options are available. We highlight those potential SIRT1 target genes that are commonly affected in pancreatic cancer according to recent genomic analyses.
