Transcription factor RTEF-1 mediates alpha1-adrenergic reactivation of the fetal gene program in cardiac myocytes

Dual function of VGLL4 in muscle regeneration

VGLL4 has previously been identified as a negative regulator of YAP. Here we show that VGLL4 regulates muscle regeneration in both YAP-dependent and YAP-independent manners at different stages. Knockout of VGLL4 in mice leads to smaller myofiber size and defective muscle contraction force. Furthermore, our studies reveal that knockout of VGLL4 results in increased muscle satellite cells proliferation and impaired myoblast differentiation, which ultimately leads to delayed muscle regeneration. Mechanistically, the results show that VGLL4 works as a conventional repressor of YAP at the proliferation stage of muscle regeneration. At the differentiation stage, VGLL4 acts as a co-activator of TEAD4 to promote MyoG transactivation and facilitate the initiation of differentiation in a YAP-independent manner. Moreover, VGLL4 stabilizes the protein-protein interactions between MyoD and TEAD4 to achieve efficient MyoG transactivation. Our findings define the dual roles of VGLL4 in regulating muscle regeneration at different stages and may open novel therapeutic perspectives for muscle regeneration.

The 9p21.3 risk locus for coronary artery disease: A 10-year search for its mechanism

The 9p21.3 risk locus is the first locus to be associated with an increased risk of coronary artery disease (CAD)-related events and many other phenotypes. This locus contains 59 single nucleotide polymorphisms (SNPs) in a region with multiple long range enhancers and long non-coding RNAs (lncRNAs) that affect the expression of neighbouring genes, cyclin-dependent kinase 2A and 2B (CDKN2A and CDKN2B), which are required for controlling vascular smooth muscle cell proliferation and ageing. Several studies have attempted to identify the precise mechanism by which this locus exerts its pathogenic effect to increase the risk of CAD-related events. In this review, we will highlight the major advances in our understanding of the genotype–phenotype correlation at the mechanistic and phenotypic levels. The high population attributable risk of the 9p21.3 risk locus, mechanistic knowledge acquired thus far, and ongoing research efforts could facilitate the design of novel therapeutic molecules to reduce the risk of CAD and its related events.

TEAD transcription factors are required for normal primary myoblast differentiation in vitro and muscle regeneration in vivo

The TEAD family of transcription factors (TEAD1-4) bind the MCAT element in the regulatory elements of both growth promoting and myogenic differentiation genes. Defining TEAD transcription factor function in myogenesis has proved elusive due to overlapping expression of family members and their functional redundancy. We show that silencing of either Tead1, Tead2 or Tead4 did not effect primary myoblast (PM) differentiation, but that their simultaneous knockdown strongly impaired differentiation. In contrast, Tead1 or Tead4 silencing impaired C2C12 differentiation showing their different contributions in PMs and C2C12 cells. Chromatin immunoprecipitation identified enhancers associated with myogenic genes bound by combinations of Tead4, Myod1 or Myog. Tead4 regulated distinct gene sets in C2C12 cells and PMs involving both activation of the myogenic program and repression of growth and signaling pathways. ChIP-seq from mature mouse muscle fibres in vivo identified a set of highly transcribed muscle cell-identity genes and sites bound by Tead1 and Tead4. Although inactivation of Tead4 in mature muscle fibres caused no obvious phenotype under normal conditions, notexin-induced muscle regeneration was delayed in Tead4 mutants suggesting an important role in myogenic differentiation in vivo. By combining knockdown in cell models in vitro with Tead4 inactivation in muscle in vivo, we provide the first comprehensive description of the specific and redundant roles of Tead factors in myogenic differentiation.

Changes in gene methylation patterns in neonatal murine hearts: Implications for the regenerative potential

Background

The neonatal murine heart is able to regenerate after severe injury; this capacity however, quickly diminishes and it is lost within the first week of life. DNA methylation is an epigenetic mechanism which plays a crucial role in development and gene expression regulation. Under investigation here are the changes in DNA methylation and gene expression patterns which accompany the loss of regenerative potential.

Results

The MeDIP-chip (methylated DNA immunoprecipitation microarray) approach was used in order to compare global DNA methylation profiles in whole murine hearts at day 1, 7, 14 and 56 complemented with microarray transcriptome profiling. We found that the methylome transition from day 1 to day 7 is characterized by the excess of genomic regions which gain over those that lose DNA methylation. A number of these changes were retained until adulthood. The promoter genomic regions exhibiting increased DNA methylation at day 7 as compared to day 1 are significantly enriched in the genes critical for heart maturation and muscle development. Also, the promoter genomic regions showing an increase in DNA methylation at day 7 relative to day 1 are significantly enriched with a number of transcription factors binding motifs including those of Mfsd6l, Mef2c, Meis3, Tead4, and Runx1.

Conclusions

The results indicate that the extensive alterations in DNA methylation patterns along the development of neonatal murine hearts are likely to contribute to the decline of regenerative capabilities observed shortly after birth. This conclusion is supported by the evidence that an increase in DNA methylation in the neonatal murine heart from day 1 to day 7 occurs in the promoter regions of genes playing important roles in cardiovascular system development.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2545-1) contains supplementary material, which is available to authorized users.

RTEF-1 protects against oxidative damage induced by H2O2 in human umbilical vein endothelial cells through Klotho activation

Oxidative stress is a main risk factor of vascular aging, which may lead to age-associated diseases. Related transcriptional enhancer factor-1 (RTEF-1) has been suggested to regulate many genes expression which are involved in the endothelial angiogenesis and vasodilation. However, whether RTEF-1 has a direct role in anti-oxidation and what specific genes are involved in RTEF-1-driven anti-oxidation have not been elucidated. In this study, we found that overexpressing RTEF-1 in H2O2-treated human umbilical vein endothelial cells decreased senescence-associated-β-galactosidase (SA-β-gal)-positive cells and G0/G1 cells population. The expressions of p53 and p21 were decreased in H2O2-treated RTEF-1 o/e human umbilical vein endothelial cells. However, specific small interfering RNA of RTEF-1 totally reversed the anti-oxidation effect of RTEF-1 and inhibited RTEF-1-induced decreased p53 and p21 expressions. It demonstrated that RTEF-1 could protect cells from H2O2-induced oxidative damage. In addition, we demonstrated that RTEF-1 could up-regulate Klotho gene expression and activate its promoter. Furthermore, Klotho small interfering RNA significantly blocked RTEF-1-driven endothelial cell protection from H2O2-induced oxidative damage and increased p53 and p21 expressions. These results reveal that RTEF-1 is a potential anti-oxidation gene and can prevent H2O2-induced endothelial cell oxidative damage by activating Klotho.

Characterization of the transcriptional activation domains of human TEF3-1 (transcription enhancer factor 3 isoform 1)

TEF3-1 (transcription enhancer factor 3 isoform 1) is a human transcriptional factor, which has a N-terminal TEA/ATTS domain supposedly for DNA binding and C-terminal PRD and STY domains for transcriptional activation. Taking advantage of the efficient reporter design of yeast two-hybrid system, we characterized the TEF3-1 domains in activating gene expression. Previously study usually mentioned that the C-terminal domain of TEF3-1 has the transcriptional activity, however, our data shows that the peptides TEF3-11-66 and TEF3-1197-434 functioned as two independent activation domains, suggesting that N-terminal domain of TEF3-1 also has transcriptional activation capacity. Additionally, more deletions of amino acids 197-434 showed that only the peptides TEF3-1197-265 contained the minimum sequences for the C-terminal transcriptional activation domain. The protein structure is predicted to contain a helix-turn-helix structure in TEF3-11-66 and four β sheets in TEF3-1197-265. Finally, after the truncated fragments of TEF3-1 were expressed in HUVEC cells, the whole TEF3-1 and the two activation domains could increase F-actin stress fiber, cell proliferation, migration and targeted gene expression. Further analysis and characterization of the activation domains in TEF3-1 may broaden our understanding of the gene involved in angiogenesis and other pathological processes.

The Huntington's disease-related cardiomyopathy prevents a hypertrophic response in the R6/2 mouse model

Huntington's disease (HD) is neurodegenerative disorder for which the mutation results in an extra-long tract of glutamines that causes the huntingtin protein to aggregate. It is characterized by neurological symptoms and brain pathology that is associated with nuclear and cytoplasmic aggregates and with transcriptional deregulation. Despite the fact that HD has been recognized principally as a neurological disease, there are multiple epidemiological studies showing that HD patients exhibit a high rate of cardiovascular events leading to heart failure. To unravel the mechanistic basis of cardiac dysfunction in HD, we employed a wide range of molecular techniques using the well-established genetic R6/2 mouse model that develop a considerable degree of the cardiac atrophy at end stage disease. We found that chronic treatment with isoproterenol, a potent beta-adrenoreceptor agonist, did not change the overall gross morphology of the HD murine hearts. However, there was a partial response to the beta-adrenergenic stimulation by the further re-expression of foetal genes. In addition we have profiled the expression level of Hdacs in the R6/2 murine hearts and found that the isoproterenol stimulation of Hdac expression was partially blocked. For the first time we established the Hdac transcriptional profile under hypertrophic conditions and found 10 out of 18 Hdacs to be markedly deregulated. Therefore, we conclude that R6/2 murine hearts are not able to respond to the chronic isoproterenol treatment to the same degree as wild type hearts and some of the hypertrophic signals are likely attenuated in the symptomatic HD animals.

Endothelial differentiation gene-1, a new downstream gene is involved in RTEF-1 induced angiogenesis in endothelial cells

Related Transcriptional Enhancer Factor-1 (RTEF-1) has been suggested to induce angiogenesis through regulating target genes. Whether RTEF-1 has a direct role in angiogenesis and what specific genes are involved in RTEF-1 driven angiogenisis have not been elucidated. We found that over-expressing RTEF-1 in Human dermal microvascular endothelial cells-1 (HMEC-1) significantly increased endothelial cell aggregation, growth and migration while the processes were inhibited by siRNA of RTEF-1. In addition, we observed that Endothelial differentiation gene-1 (Edg-1) expression was up-regulated by RTEF-1 at the transcriptional level. RTEF-1 could bind to Edg-1 promoter and subsequently induce its activity. Edg-1 siRNA significantly blocked RTEF-1-driven increases in endothelial cell aggregation in a Matrigel assay and retarded RTEF-1-induced endothelial cell growth and migration. Pertussis Toxin (PTX), a Gi/Go protein sensitive inhibitor, was found to inhibit RTEF-1 driven endothelial cell aggregation and migration. Our data demonstrates that Edg-1 is a potential target gene of RTEF-1 and is involved in RTEF-1-induced angiogenesis in endothelial cells. Gi/Go protein coupled receptor pathway plays a role in RTEF-1 driven angiogenesis in endothelial cells.

Structural and functional analysis of the related transcriptional enhancer factor-1 and NF-κB interaction

The related transcriptional enhancer factor-1 (RTEF-1) increases gene transcription of hypoxia-inducible factor 1α (HIF-1α) and enhances angiogenesis in endothelium. Both hypoxia and inflammatory factor TNF-α regulate gene expression of HIF-1α, but how RTEF-1 and TNF-α coordinately regulate HIF-1α gene transcription is unclear. Here, we found that RTEF-1 interacts with p65 subunit of NF-κB, a primary mediator of TNF-α. RTEF-1 increased HIF-1α promoter activity, whereas expression of p65 subunit inhibited the stimulatory effect. By contrast, knockdown of p65 markedly enhanced RTEF-1 stimulation on the HIF-1α promoter activity (7-fold). A physical interaction between RTEF-1 and p65 was confirmed by coimmunoprecipitation experiments in cells and glutathione S-transferase (GST)-pull-down assays. A computational analysis of RTEF-1 crystal structures revealed that a conserved surface of RTEF-1 potentially interacts with p65 via four amino acid residues located at T347, Y349, R351, and Y352. We performed site-directed mutagenesis and GST-pull-down assays and demonstrated that Tyr352 (Y352) in RTEF-1 is a key site for the formation of RTEF-1 and p65-NF-κB complex. An alanine mutation at Y352 of RTEF-1 disrupted the interaction of RTEF-1 with p65. Moreover, expression of RTEF-1 decreased TNF-α-induced HIF-1α promoter activity, IL-1β, and IL-6 mRNA levels in cells; however, the effect of RTEF-1 was largely lost when Y352 was mutated to alanine. These results indicate that RTEF-1 interacts with p65-NF-κB through Y352 and that they antagonize each other for HIF-1α transcriptional activation, suggesting a novel mechanism by which RTEF-1 regulates gene expression, linking hypoxia to inflammation.

Sequencing of mRNA identifies re-expression of fetal splice variants in cardiac hypertrophy

Cardiac hypertrophy has been well-characterized at the level of transcription. During cardiac hypertrophy, genes normally expressed primarily during fetal heart development are re-expressed, and this fetal gene program is believed to be a critical component of the hypertrophic process. Recently, alternative splicing of mRNA transcripts has been shown to be temporally regulated during heart development, leading us to consider whether fetal patterns of splicing also reappear during hypertrophy. We hypothesized that patterns of alternative splicing occurring during heart development are recapitulated during cardiac hypertrophy. Here we present a study of isoform expression during pressure-overload cardiac hypertrophy induced by 10 days of transverse aortic constriction (TAC) in rats and in developing fetal rat hearts compared to sham-operated adult rat hearts, using high-throughput sequencing of poly(A) tail mRNA. We find a striking degree of overlap between the isoforms expressed differentially in fetal and pressure-overloaded hearts compared to control: forty-four percent of the isoforms with significantly altered expression in TAC hearts are also expressed at significantly different levels in fetal hearts compared to control (P<0.001). The isoforms that are shared between hypertrophy and fetal heart development are significantly enriched for genes involved in cytoskeletal organization, RNA processing, developmental processes, and metabolic enzymes. Our data strongly support the concept that mRNA splicing patterns normally associated with heart development recur as part of the hypertrophic response to pressure overload. These findings suggest that cardiac hypertrophy shares post-transcriptional as well as transcriptional regulatory mechanisms with fetal heart development.

The role of transcription enhancer factors in cardiovascular biology

The transcriptional enhancer factor (TEF) multigene family is primarily functional in muscle-specific genes through binding to MCAT elements that activate or repress transcription of many genes in response to physiological and pathological stimuli. Among the TEF family, TEF-1, RTEF-1, and DTEF-1 are critical regulators of cardiac and smooth muscle-specific genes during cardiovascular development and cardiac disorders including cardiac hypertrophy. Emerging evidence suggests that in addition to functioning as muscle-specific transcription factors, members of the TEF family may be key mediators of gene expression induced by hypoxia in endothelial cells by virtue of its multidomain organization, potential for post-translational modifications, and interactions with numerous transcription factors, which represent a cell-selective control mediator of nuclear signaling. We review the recent literature demonstrating the involvement of the TEF family of transcription factors in the regulation of differential gene expression in cardiovascular physiology and pathology.

An introduction to murine models of atrial fibrillation

Understanding the mechanism of re-entrant arrhythmias in the past 30 years has allowed the development of almost curative therapies for many rhythm disturbances. The complex, polymorphic arrhythmias of atrial fibrillation (AF) and sudden death are, unfortunately, not yet well understood, and hence still in need of adequate therapy. AF contributes markedly to morbidity and mortality in aging Western populations. In the past decade, many genetically altered murine models have been described and characterized. Here, we review genetically altered murine models of AF; powerful tools that will enable a better understanding of the mechanisms of AF and the assessment of novel therapeutic interventions.

Genome-wide mapping of Sox6 binding sites in skeletal muscle reveals both direct and indirect regulation of muscle terminal differentiation by Sox6

Background

Sox6 is a multi-faceted transcription factor involved in the terminal differentiation of many different cell types in vertebrates. It has been suggested that in mice as well as in zebrafish Sox6 plays a role in the terminal differentiation of skeletal muscle by suppressing transcription of slow fiber specific genes. In order to understand how Sox6 coordinately regulates the transcription of multiple fiber type specific genes during muscle development, we have performed ChIP-seq analyses to identify Sox6 target genes in mouse fetal myotubes and generated muscle-specific Sox6 knockout (KO) mice to determine the Sox6 null muscle phenotype in adult mice.

Results

We have identified 1,066 Sox6 binding sites using mouse fetal myotubes. The Sox6 binding sites were found to be associated with slow fiber-specific, cardiac, and embryonic isoform genes that are expressed in the sarcomere as well as transcription factor genes known to play roles in muscle development. The concurrently performed RNA polymerase II (Pol II) ChIP-seq analysis revealed that 84% of the Sox6 peak-associated genes exhibited little to no binding of Pol II, suggesting that the majority of the Sox6 target genes are transcriptionally inactive. These results indicate that Sox6 directly regulates terminal differentiation of muscle by affecting the expression of sarcomere protein genes as well as indirectly through influencing the expression of transcription factors relevant to muscle development. Gene expression profiling of Sox6 KO skeletal and cardiac muscle revealed a significant increase in the expression of the genes associated with Sox6 binding. In the absence of the Sox6 gene, there was dramatic upregulation of slow fiber-specific, cardiac, and embryonic isoform gene expression in Sox6 KO skeletal muscle and fetal isoform gene expression in Sox6 KO cardiac muscle, thus confirming the role Sox6 plays as a transcriptional suppressor in muscle development.

Conclusions

Our present data indicate that during development, Sox6 functions as a transcriptional suppressor of fiber type-specific and developmental isoform genes to promote functional specification of muscle which is critical for optimum muscle performance and health.

Requirement of the nuclear localization of transcription enhancer factor 3 for proliferation, migration, tube formation, and angiogenesis induced by vascular endothelial growth factor

Transcription enhancer factor 3 (TEF3) is known to regulate the expression of muscle-specific genes and to play important roles in muscle development and diseases. However, little is known about its role in vascular endothelial growth factor (VEGF)-induced angiogenesis. Most recently, we discovered a novel function of TEF3, in which TEF3 is required for the up-regulation of a proangiogenic factor, Down syndrome candidate region 1 isoform 1L (DSCR1-1L), induced by VEGF-A(165) in endothelial cells. Overexpression of TEF3 isoform 1 (TEF3-1) is sufficient to induce DSCR1-1L expression. Here, we report that knocking down the expression of TEF3 almost completely inhibits VEGF-A(165)-induced proliferation, migration, tube formation, formation of F-actin stress fiber, and in vivo Matrigel angiogenesis. This inhibition cannot be rescued by DSCR1-1L overexpression. Further, overexpression of TEF3-1, but not its nuclear localization signal-deletion mutant (TEF3-ΔNLS), induces human umbilical vein endothelial cell proliferation, migration, tube formation, and formation of F-actin stress fiber, even in the absence of VEGF-A(165) stimulation, which is partially inhibited by DSCR1-1L silencing. Our data demonstrate that TEF3, mainly its nuclear localization, is required for VEGF-A(165)-induced endothelial proliferation, migration, tube formation, and in vivo Matrigel angiogenesis.

IRF2BP2 is a skeletal and cardiac muscle-enriched ischemia-inducible activator of VEGFA expression

We sought to identify an essential component of the TEAD4/VGLL4 transcription factor complex that controls vascular endothelial growth factor A (VEGFA) expression in muscle. A yeast 2-hybrid screen was used to clone a novel component of the TEAD4 complex from a human heart cDNA library. We identified interferon response factor 2 binding protein 2 (IRF2BP2) and confirmed its presence in the TEAD4/VGLL4 complex in vivo by coimmunoprecipitation and mammalian 2-hybrid assays. Coexpression of IRF2BP2 with TEAD4/VGLL4 or TEAD1 alone potently activated, whereas knockdown of IRF2BP2 reduced, VEGFA expression in C(2)C(12) muscle cells. Thus, IRF2BP2 is required to activate VEGFA expression. In mouse embryos, IRF2BP2 was ubiquitously expressed but became progressively enriched in the fetal heart, skeletal muscles, and lung. Northern blot analysis revealed high levels of IRF2BP2 mRNA in adult human heart and skeletal muscles, but immunoblot analysis showed low levels of IRF2BP2 protein in skeletal muscle, indicating post-transcriptional regulation of IRF2BP2 expression. IRF2BP2 protein levels are markedly increased by ischemia in skeletal and cardiac muscle compared to normoxic controls. IRF2BP2 is a novel ischemia-induced coactivator of VEGFA expression that may contribute to revascularization of ischemic cardiac and skeletal muscles.

TEAD-1 overexpression in the mouse heart promotes an age-dependent heart dysfunction

TEA domain transcription factor-1 (TEAD-1) is essential for proper heart development and is implicated in cardiac specific gene expression and the hypertrophic response of primary cardiomyocytes to hormonal and mechanical stimuli, and its activity increases in the pressure-overloaded hypertrophied rat heart. To investigate whether TEAD-1 is an in vivo modulator of cardiac specific gene expression and hypertrophy, we developed transgenic mice expressing hemagglutinin-tagged TEAD-1 under the control of the muscle creatine kinase promoter. We show that a sustained increase in TEAD-1 protein leads to an age-dependent dysfunction. Magnetic resonance imaging revealed decreases in cardiac output, stroke volume, ejection fraction, and fractional shortening. Isolated TEAD-1 hearts revealed decreased left ventricular power output that correlated with increased betaMyHC protein. Histological analysis showed altered alignment of cardiomyocytes, septal wall thickening, and fibrosis, although electrocardiography displayed a left axis shift of mean electrical axis. Transcripts representing most members of the fetal heart gene program remained elevated from fetal to adult life. Western blot analyses revealed decreases in p-phospholamban, SERCA2a, p-CX43, p-GSK-3alpha/beta, nuclear beta-catenin, GATA4, NFATc3/c4, and increased NCX1, nuclear DYKR1A, and Pur alpha/beta protein. TEAD-1 mice did not display cardiac hypertrophy. TEAD-1 mice do not tolerate stress as they die over a 4-day period after surgical induction of pressure overload. These data provide the first in vivo evidence that increased TEAD-1 can induce characteristics of cardiac remodeling associated with cardiomyopathy and heart failure.

Regulation and significance of atrial and brain natriuretic peptides as cardiac hormones

Atrial and brain natriuretic peptides (ANP and BNP, respectively) are cardiac hormones. During cardiac development, their expression is a maker of cardiomyocyte differentiation and is under tight spatiotemporal regulation. After birth, however, their ventricular expression is only up-regulated in response to various cardiovascular diseases. As a result, analysis of ANP and BNP gene expression has led to discoveries of transcriptional regulators and signaling pathways involved in both cardiac differentiation and cardiac disease. Studies using genetically engineered mice have shed light on the molecular mechanisms regulating ANP and BNP gene expression, as well as the physiological and pathophysiological relevance of the cardiac natriuretic peptide system. In this review we will summarize what is currently known about their regulation and the significance of ANP and BNP as hormones derived from the heart.

The transcriptional co-activator TAZ interacts differentially with transcriptional enhancer factor-1 (TEF-1) family members

Members of the highly related TEF-1 (transcriptional enhancer factor-1) family (also known as TEAD, for TEF-1, TEC1, ABAA domain) bind to MCAT (muscle C, A and T sites) and A/T-rich sites in promoters active in cardiac, skeletal and smooth muscle, placenta, and neural crest. TEF-1 activity is regulated by interactions with transcriptional co-factors [p160, TONDU (Vgl-1, Vestigial-like protein-1), Vgl-2 and YAP65 (Yes-associated protein 65 kDa)]. The strong transcriptional co-activator YAP65 interacts with all TEF-1 family members, and, since YAP65 is related to TAZ (transcriptional co-activator with PDZ-binding motif), we wanted to determine if TAZ also interacts with members of the TEF-1 family. In the present study, we show by GST (glutathione S-transferase) pull-down assays, by co-immunoprecipitation and by modified mammalian two-hybrid assays that TEF-1 interacts with TAZ in vitro and in vivo. Electrophoretic mobility-shift assays with purified TEF-1 and GST-TAZ fusion protein showed that TAZ interacts with TEF-1 bound to MCAT DNA. TAZ can interact with endogenous TEF-1 proteins, since exogenous TAZ activated MCAT-dependent reporter promoters. Like YAP65, TAZ interacted with all four TEF-1 family members. GST pull-down assays with increasing amounts of [35S]TEF-1 and [35S]RTEF-1 (related TEF-1) showed that TAZ interacts more efficiently with TEF-1 than with RTEF-1. This differential interaction also extended to the interaction of TEF-1 and RTEF-1 with TAZ in vivo, as assayed by a modified mammalian two-hybrid experiment. These data show that differential association of TEF-1 proteins with transcriptional co-activators may regulate the activity of TEF-1 family members.

Enhancer of polycomb1 acts on serum response factor to regulate skeletal muscle differentiation

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 p300 to induce skeletal muscle differentiation. Epc1 interacted physically with SRF. Transfection of Epc1 to myoblast cells potentiated the SRF-induced expression of skeletal muscle-specific genes as well as multinucleation. Proximal CArG box in the skeletal alpha-actin promoter was responsible for the synergistic activation of the promoter-luciferase. Epc1 knockdown caused a decrease in the acetylation of histones associated with serum response element (SRE) of the skeletal alpha-actin promoter. The Epc1.SRF complex bound to the SRE, and the knockdown of Epc1 resulted in a decrease in SRF binding to the skeletal alpha-actin promoter. Epc1 recruited histone acetyltransferase activity, which was potentiated by cotransfection with p300 but abolished by si-p300. Epc1 directly bound to p300 in myoblast cells. Epc1+/- mice showed distortion of skeletal alpha-actin, and the isolated myoblasts from the mice had impaired muscle differentiation. These results suggest that Epc1 is required for skeletal muscle differentiation by recruiting both SRF and p300 to the SRE of muscle-specific gene promoters.

Expression of S100A6 in cardiac myocytes limits apoptosis induced by tumor necrosis factor-alpha

S100A6 is induced in myocardium post-infarction in vivo and in response to growth factors and inflammatory cytokines in vitro. Forced expression of S100A6 in cardiomyocytes inhibits regulation of cardiac specific gene expression in response to trophic stimulation. To define regulation and function of S100A6, we characterized the human S100A6 promoter and mapped upstream regulatory elements in rat neonatal cardiac myocytes, fibroblasts, and vascular smooth muscle cells and defined a functional role for S100A6 in tumor necrosis factor-alpha-induced myocyte apoptosis. The functional S100A6 promoter was localized to region -167/+134 containing 167 upstream base pairs. The S100A6 promoter is regulated by positive (-361/-167 and -588/-361) and negative (-1371/-1194) elements. Tumor necrosis factor-alpha induced the maximal S100A6 promoter and transcription factor NF-kappaB (p65 subunit). Electrophoretic mobility shift showed that tumor necrosis factor-alpha induced p65 binding to a potential NF-kappaB-binding site at -460/-451. Chromatin immunoprecipitation analysis revealed p65 is recruited to the S100A6 promoter upon tumor necrosis factor-alpha stimulation. The NF-kappaB inhibitor caffeic acid phenethyl ester and mutation of the NF-kappaB-binding site inhibited S100A6 promoter activation by tumor necrosis factor-alpha. Tumor necrosis factor-alpha induced cardiac myocyte apoptosis. Specific inhibition of S100A6 using a small interfering RNA directed against S100A6 potentiated tumor necrosis factor-alpha-induced myocyte apoptosis, whereas overexpression of S100A6 by gene transfer prevented tumor necrosis factor-alpha-induced myocyte apoptosis by interfering with p53 phosphorylation. These results demonstrate that S100A6 is induced by tumor necrosis factor-alpha via an NF-kappaB-dependent mechanism, serving a role in homeostasis to limit tumor necrosis factor-alpha-induced apoptosis by regulating p53 phosphorylation.

Transcription enhancer factor 3 (TEF3) mediates the expression of Down syndrome candidate region 1 isoform 1 (DSCR1-1L) in endothelial cells

The Down syndrome candidate region 1 gene (DSCR1) can be expressed as four isoforms, one of which is the well-studied isoform 4 (DSCR1-4) that is induced by VEGF-A(165) to provide a negative feedback loop in the VEGF-A(165)-induced angiogenesis. We reported previously that another DSCR1 isoform, DSCR1-1L, was also up-regulated by VEGF-A(165) in cultured endothelial cells and in several in vivo models of pathological angiogenesis and that different from DSCR1-4, DSCR1-1L overexpression alone induced cultured endothelial cell proliferation and promoted angiogenesis in Matrigel assays. It was reported recently that tumor growth was greatly repressed in DSCR1 knock-out mice. Although DSCR1-4 transcription was primarily regulated by NFAT, the mechanism regulating DSCR1-1L expression was still unknown. We developed human DSCR1-1L promoter-driven luciferase system and found that deletion of a putative conserved M-CAT site located 1426-bp upstream of the translation start site blunted promoter activity. We further showed that knockdown of TEF3, not other members of TEF family inhibited VEGF-A(165)-induced DSCR1-1L expression. We also demonstrated that TEF3 directly interacted with the putative M-CAT site in the DSCR1-1L promoter in vitro and in vivo. Finally, overexpression of TEF3 isoform 1, not isoform 3, in HUVEC was sufficient to induce DSCR1-1L expression even in the absence of VEGF-A(165) stimulation. Taken together, we elucidated a novel function of transcriptional factor TEF3. TEF3 was required for DSCR1-1L expression through binding to the M-CAT site in its promoter and could be an attractive target for anti-angiogenesis therapy.

Myocyte-specific M-CAT and MEF-1 elements regulate G-protein gamma 3 gene (gamma3) expression in cardiac myocytes

Little is known regarding the mechanisms that control the expression of G-protein alpha, beta, and gamma subtypes. We have previously shown that the G-protein gamma(3) gene is expressed in the heart, brain, lung, spleen, kidney, muscle, and testis in mice. We have also reported that the G-protein gamma(3) subunit is expressed in rat cardiac myocytes, but not in cardiac fibroblasts. Other studies have shown that the gamma(3) subunit couples to the angiotensin A1A receptor in portal vein myocytes, and has been shown to mediate beta-adrenergic desensitization in cardiac myocytes treated with atorvastatin. In the present study, we evaluated G-protein gamma(3) promoter-luciferase reporter constructs in primary myocytes to identify key regulatory promoter regions. We identified two important regions of the promoter (upstream promoter region [UPR] and downstream promoter region [DPR]), which are required for expression in cardiac myocytes. We observed that removal of 48 bp in the UPR diminished gene transcription by 75%, and that the UPR contains consensus elements for myocyte-specific M-CAT and myocyte enhancer factor 1 (MEF-1) elements. The UPR and DPR share transcription factor elements for myocyte-specific M-CAT element. We observed that cardiac myocyte proteins bind to gamma(3) oligonucleotides containing transcription factor elements for myocyte-specific M-CAT and MEF-1. Myocyte-specific M-CAT proteins were supershifted with transcriptional enhancer factor-1 (TEF-1) antibodies binding to the gamma(3) M-CAT element, which is in agreement with reports showing that the M-CAT element binds the TEF-1 family of transcription factors. The 150 bp DPR contains three M-CAT elements, an INR element, an upstream stimulatory factor 1 element, and the transcription start site. We have shown that myocyte gamma(3) gene expression is regulated by myocyte-specific M-CAT and MEF-1 elements.

Porcine TEF1 and RTEF1: molecular characterization and association analyses with growth traits

TEA domain transcription factors play vital roles in myogenesis by binding the M-CAT motif in the promoter of the muscle-specific genes. In the present study, we cloned two porcine TEA domain family genes, TEF1 and RTEF1, and identified two different variants respectively. RT-PCR revealed that the TEF1-a variant was highly expressed and up-regulated with the development of the porcine skeletal muscle, indicating its potential regulatory function for muscle development. Promoter analysis revealed porcine TEF1 was regulated, in a TATA-independent manner, by a specific intact initiator element, and numerous binding motifs of multiple transcription factors, including SP1, CREB/ATF and AREB6. A substitution G93A was identified in the 5'-flanking sequence and used for the linkage mapping of TEF1. Association analyses in a BerkshirexYorkshire F(2) population revealed that the substitution of G93A has a significant effect on average daily gain from birth to weaning (p<0.05) and 16-day weight (p<0.05), and a suggestive effect on loin eye area (p<0.06), average back fat (p<0.07) and lumbar back fat (p<0.08). The association analyses results are in agreement with the gene's localization demonstrated by linkage analysis, SCHP and RH mapping to the QTL region of growth and carcass traits on chromosome 2p14-17.

Factors controlling cardiac myosin-isoform shift during hypertrophy and heart failure

Myosin is a molecular motor, which interacts with actin to convert the energy from ATP hydrolysis into mechanical work. In cardiac myocytes, two myosin isoforms are expressed and their relative distribution changes in different developmental and pathophysiologic conditions of the heart. It has been realized for a long time that a shift in myosin isoforms plays a major role in regulating myocardial contractile activity. With the recent evidence implicating that alteration in myosin isoform ratio may be eventually beneficial for the treatment of a stressed heart, a new interest has developed to find out ways of controlling the myosin isoform shift. This article reviews the published data describing the role of myosin isoforms in the heart and highlighting the importance of various factors shown to influence myosin isofrom shift during physiology and disease states of the heart.

Characterization of cardiac gene promoter activity: reporter constructs and heterologous promoter studies

Cardiac gene promoter analysis remains an integral method in molecular cardiology and continues to provide novel insights into the transcriptional mechanisms that regulate gene expression in the myocardium. Initial studies focused on the regulated expression of contractile genes, since their transcripts are abundant and their cDNAs were among the first to be cloned. More recent studies have focused on the promoters of genes expressed at much lower levels, including those that encode ion channels, signaling proteins, and the cardiac transcription factors. The standard approach to analyze myocardial gene promoters has been to transfect reporter plasmids into cultured neonatal rat cardiac myocytes. This approach has the unique advantage of allowing the exploration of different signaling mechanisms by supplementing culture media with different agonists and inhibitors. In addition, cis-elements that control gene expression under different physiological stresses have been further characterized in the context of heterologous promoters to demonstrate their "stand-alone" functional properties in the absence of confounding influences from other cis-elements and their cognate transcription factors. Here we illustrate the characterization of cardiac gene promoter activity using reporter constructs and heterologous promoter studies in cultured cardiac myocytes.

Re-employment of developmental transcription factors in adult heart disease

A finite number of transcription factors constitute a combinatorial code that orchestrates cardiac development and the specification and differentiation of myocytes. Many, if not all of these same transcription factors are re-employed in the adult heart in response to disease stimuli that promote hypertrophic enlargement and/or dilated cardiomyopathy, as part of the so-called "fetal gene program". This review will discuss the transcription factors that regulate the hypertrophic growth response of the adult heart, with a special emphasis on those regulators that participate in cardiac development.

Transcription Enhancer Factor-1-dependent Expression of the α-Tropomyosin Gene in the Three Muscle Cell Types

In vertebrates, the actin-binding proteins tropomyosins are encoded by four distinct genes that are expressed in a complex pattern during development and muscle differentiation. In this study, we have characterized the transcriptional machinery of the alpha-tropomyosin (alpha-Tm) gene in muscle cells. Promoter analysis revealed that a 284-bp proximal promoter region of the Xenopus laevis alpha-Tm gene is sufficient for maximal activity in the three muscle cell types. The transcriptional activity of this promoter in the three muscle cell types depends on both distinct and common cis-regulatory sequences. We have identified a 30-bp conserved sequence unique to all vertebrate alpha-Tm genes that contains an MCAT site that is critical for expression of the gene in all muscle cell types. This site can bind transcription enhancer factor-1 (TEF-1) present in muscle cells both in vitro and in vivo. In serum-deprived differentiated smooth muscle cells, TEF-1 was redistributed to the nucleus, and this correlated with increased activity of the alpha-Tm promoter. Overexpression of TEF-1 mRNA in Xenopus embryonic cells led to activation of both the endogenous alpha-Tm gene and the exogenous 284-bp promoter. Finally, we show that, in transgenic embryos and juveniles, an intact MCAT sequence is required for correct temporal and spatial expression of the 284-bp gene promoter. This study represents the first analysis of the transcriptional regulation of the alpha-Tm gene in vivo and highlights a common TEF-1-dependent regulatory mechanism necessary for expression of the gene in the three muscle lineages.

Regulation of testis-specific carnitine transporter (octn3) gene by proximal cis-acting elements Sp1 in mice

The mouse octn transporter family consists of three genes, octn1, octn2 and octn3. The gene products octn2 and octn3, which transport carnitine with high affinity, are both expressed in testis, where carnitine is required to maintain sperm cell motility. Here, we focused on the regulatory mechanism of the expression of octn3 in an attempt to determine whether the differential tissue expression profiles of the octn2 and octn3 genes reflect distinct physiological roles of octn2 and octn3. The promoter activity of the octn3 gene was examined by luciferase assay and gel mobility shift assay using the mouse Sertoli cell line TM4 as host cells. Deletion-mutant assay demonstrated that a gene segment of the 5'-untranslated region located at about -500 bp relative to the transcription start site is required for constitutive octn3 transcription. Deletion of the Sp1-binding site within the region resulted in loss of transcriptional activity. In addition, overexpression of Sp1 in TM4 cells led to a further increase of transcription of octn3. These results demonstrated that Sp1-binding sites are necessary and sufficient for constitutive octn3 gene transcription. Furthermore, the expressions of both of octn2 and octn3 genes in TM4 cells were up-regulated by palmitic acid, whereas carnitine increased only the expression of octn2 without any change in octn3 expression. Accordingly, the expressions of octn2 and 3 are regulated by distinct mechanisms, suggesting distinct roles of octn2 and octn3 in carnitine transport.

Nitric oxide inhibits endothelin-1-induced cardiomyocyte hypertrophy through cGMP-mediated suppression of extracellular-signal regulated kinase phosphorylation

Cardiac hypertrophy is a compensatory mechanism in response to a variety of cardiovascular diseases. Recently, reactive oxygen species and nitric oxide (NO) have been demonstrated to be involved in the pathogenesis of atherosclerosis; however, the role of these free radicals in the development of cardiac hypertrophy remains unclear. In this study, we investigate NO modulation of cellular signaling in endothelin-1 (ET-1)-induced cardiomyocyte hypertrophy in culture. ET-1 treatment of cardiomyocytes increased constitutive NO synthase activity and induced NO production via the stimulation of ET-receptor subtype ET(B). Using Northern blot analysis and chloramphenicol acetyltransferase assay, we found that NO suppressed the ET-1-induced increase in c-fos mRNA level and promoter activity. In contrast, ET-1 stimulation of c-fos expression was augmented by depletion of endogenous NO generation with the addition of NO scavenger PTIO into cardiomyocytes. Cells cotransfected with the dominant negative and positive mutants of signaling molecules revealed that the Ras/Raf/extracellular-signal regulated kinase (ERK) signaling pathway is involved in ET-induced c-fos gene expression. Furthermore, NO directly inhibited ET-1-induced ERK phosphorylation and activation in a cGMP-dependent manner, indicating that NO modulates ET-1-induced c-fos expression via its inhibitory effect on ERK signaling pathway. The ET-1-stimulated activator protein-1 (AP-1) DNA binding activity and AP-1-mediated reporter activity were attenuated by NO. In addition, NO also significantly inhibited ET-1-stimulated promoter activity of hypertrophic marker gene beta-myosin heavy chain and the enhanced protein synthesis. Taken together, our findings provide the molecular basis of NO as a negative regulator in ET-1-induced cardiac hypertrophy.

Molecular regulation of the brain natriuretic peptide gene

After brain natriuretic peptide (BNP) was isolated in 1988, rapid progress was made in cloning its cDNA and gene, facilitating studies of tissue-specific expression and molecular regulation of gene expression. This review focuses on the molecular determinants of regulation of the rat and human BNP genes, including signaling pathways that impact on changes in gene expression and cis regulatory elements responsive to these signaling pathways. For both rat and human genes, elements in the proximal promoter (-124 to -80), including GATA, MCAT, and AP-1-like, have been shown to contribute to basal and inducible regulation. More distal elements in the human BNP gene respond to calcium signals (an NF-AT site at -927), thyroid hormone (a thyroid-responsive element at -1000), and mechanical stretch (shear stress-responsive elements at -652 and -162). Understanding how BNP is regulated by signaling molecules that are activated in the hypertrophied and ischemic heart should be useful in understanding the underlying pathology. This may lead to therapeutic strategies that prevent hypertrophy while allowing for the beneficial effects of BNP production.

Transcription cofactor Vgl-2 is required for skeletal muscle differentiation

TEF-1 transcription factors regulate gene expression in skeletal muscle but are not muscle-specific. Instead, TEF-1 factors rely on the muscle-specific cofactor Vestigial-like 2 (Vgl-2), a protein related to Drosophila vestigial. Previously, we showed that Vgl-2 promotes skeletal muscle differentiation and activates muscle-specific promoters. However, the mechanism whereby Vgl-2 regulates TEF-1 factors and the requirement for Vgl-2 for muscle-specific gene expression were not known. In Drosophila, vestigial alters DNA binding specificity of the TEF-1 homolog scalloped to drive wing and flight muscle-specific gene expression. Here, gel mobility shift assays show that Vgl-2 differentially affects DNA binding of different TEF-1 factors. Using an antisense morpholino, we blocked the expression of Vgl-2 and a muscle-specific gene in the myogenic C2C12 cell line and in chick embryos by electroporation. These results demonstrate that Vgl-2 is required for muscle gene expression, in part by switching DNA binding of TEF-1 factors during muscle differentiation.

Genes for left ventricular hypertrophy

Left ventricular (LV) hypertrophy is very common, particularly among hypertensives. The presence of LV hypertrophy profoundly affects morbidity and mortality from cardiovascular diseases and stroke, and is now recognized as the most important predictor of chronic heart failure. Hypertension, obesity, and diabetes are important determinants of LV hypertrophy, but they fail to identify many individuals with the condition, suggesting that other factors, likely genetic in origin, play a role. Although much research has been undertaken to understand the causes of hypertrophy and the medical treatments that can lead to its regression, much remains unknown about its genetic basis. LV hypertrophy is considered a complex genetic disease, likely representing an interaction of several genes with the environment. The heritability of LV mass, measured as a quantitative trait, falls between 0.3 and 0.7 in different populations, suggesting it has a familial component. Genes encoding proteins involved in LV structure, as well as genes encoding cell signal transduction, hormones, growth factors, calcium homeostasis, substrate metabolism, and blood pressure are likely candidates for the development of common forms of LV hypertrophy. An overview of the pathophysiology of LV hypertrophy and dysfunction is provided, in addition to evidence of the genetic basis for LV hypertrophy in humans and animal models.

Vgl-4, a Novel Member of the Vestigial-like Family of Transcription Cofactors, Regulates α1-Adrenergic Activation of Gene Expression in Cardiac Myocytes

Cardiac and skeletal muscle genes are regulated by the transcriptional enhancer factor (TEF-1) family of transcription factors. In skeletal muscle, TEF-1 factors interact with a skeletal muscle-specific cofactor called Vestigial-like 2 (Vgl-2) that is related to the Drosophila protein Vestigial. Here, we characterize Vgl-4, the only member of the Vestigial-like family expressed in the heart. Unlike other members of the Vgl family that have a single TEF-1 interaction domain called the tondu (TDU) motif, Vgl-4 has two TDU motifs in its carboxyl-terminal domain. Like other Vgl factors, Vgl-4 physically interacts with TEF-1 in an immunoprecipitation assay. Vgl-4 functionally interacts with TEF-1 and also with myocyte enhancer factor 2 in a mammalian two-hybrid assay. Overexpression of Vgl-4 in cardiac myocytes interfered with the basal expression and alpha1-adrenergic receptor-dependent activation of a TEF-1-dependent skeletal alpha-actin promoter. In cardiac myocytes cultured in serum and in serum-free medium, a myc-tagged Vgl-4 protein was located in the nucleus and cytoplasm but was exported from the nucleus when cells were treated with alpha1-adrenergic receptor agonist. A chimeric nuclear-retained Vgl-4 protein inhibited alpha1-adrenergic receptor-dependent activation. In contrast, deletion of the TDU motifs of Vgl-4 prevented Vgl-4 nuclear localization, relieved Vgl-4 interference of basal activity, and enhanced alpha1-adrenergic up-regulation of the skeletal alpha-actin promoter. Nuclear export of Vgl-4 is dependent on the nuclear exportin CRM-1. These results suggest that Vgl-4 modulates the activity of TEF-1 factors and counteracts alpha1-adrenergic activation of gene expression in cardiac myocytes.

RTEF-1, a Novel Transcriptional Stimulator of Vascular Endothelial Growth Factor in Hypoxic Endothelial Cells

Vascular endothelial growth factor (VEGF) is an angiogenic growth factor known to be up-regulated in ischemic heart and hypoxic endothelial cells. However, the transcriptional regulation of VEGF in hypoxia-induced angiogenesis is not fully understood. Transcriptional enhancer factor-1 (TEF-1) is a transcriptional factor family that can regulate many genes expressed in cardiac and skeletal muscle cells by binding to myocyte-specific chloramphenicol acetyltransferase heptamer elements in the promoters of these genes. In this study, we demonstrated that related TEF-1 (RTEF-1), a member of the TEF-1 family, is up-regulated in hypoxic endothelial cells. Overexpression of RTEF-1 increases VEGF promoter activity and VEGF expression. Sequential deletion and site-directed mutation analyses of the VEGF promoter demonstrated that a GC-rich region containing four Sp1 response elements, located between -114 and -50, was essential for RTEF-1 function. This region is beyond the hypoxia-inducible factor-1alpha binding site and does not consist of M-CAT-related elements. By electrophoretic mobility shift assay, RTEF-1 was found to interact with the first Sp1 residue (-97 to -87) of the four consecutive Sp1 elements. Binding activity of RTEF-1 to VEGF promoter is also confirmed by chromatin immunoprecipitation. In addition, induction of VEGF promoter activity by RTEF-1 results in an increase of angiogenic processes including endothelial cells proliferation and vascular structure formation. These results indicate that RTEF-1 acts as a transcriptional stimulator of VEGF by regulating VEGF promoter activity through binding to Sp1 site. In addition, RTEF-1-induced VEGF promoter activity was enhanced in a hypoxic condition, indicating that RTEF-1 may play an important role in the regulation of VEGF under hypoxia.

Identification of minimal enhancer elements sufficient for Pax3 expression in neural crest and implication of Tead2 as a regulator of Pax3

Pax3 is a transcription factor that is required by Pre-migratory neural crest cells give rise to the peripheral nervous system, melanocytes, some vascular smooth muscle, and numerous other derivatives. These cells require the transcription factor Pax3, and both mice and humans with Pax3 deficiency exhibit neural crest-related developmental defects. Pax3 is also expressed in the dorsal neural tube, and by myogenic progenitors in the presomitic mesoderm and the hypaxial somites. Molecular pathways that regulate Pax3expression in the roof plate probably represent early upstream signals in neural crest induction. We have identified an enhancer region in the Pax3 genomic locus that is sufficient to recapitulate expression in neural crest precursors in transgenic mice. We show that Tead2, a member of the Tead box family of transcription factors, binds to a neural crest enhancer and activates Pax3 expression. Tead2, and its co-activator YAP65, are co-expressed with Pax3 in the dorsal neural tube, and mutation of the Tead2 binding site in the context of Pax3 transgenic constructs abolishes neural expression. In addition, a Tead2-Engrailed fusion protein is able to repress retinoic acid-induced Pax3 expression in P19 cells and in vivo. These results suggest that Tead2 is an endogenous activator of Pax3 in neural crest.

Transcriptional regulation of the type I myosin heavy chain gene in denervated rat soleus

Denervation (DEN) of rat soleus is associated with a decreased expression of slow type I myosin heavy chain (MHC) and an increased expression of the faster MHC isoforms. The molecular mechanisms behind these shifts remain unclear. We first investigated endogenous transcriptional activity of the type I MHC gene in normal and denervated soleus muscles via pre-mRNA analysis. Our results suggest that the type I MHC gene is regulated via transcriptional processes in the denervated soleus. Deletion and mutational analysis of the rat type I MHC promoter was then used to identify cis elements or regions of the promoter involved in this response. DEN significantly decreased in vivo activity of the -3,500, -2,500, -914, -408, -299, and -215 bp type I MHC promoters, relative to the alpha-skeletal actin promoter. In contrast, normalized -171 promoter activity was unchanged. Mutation of the betae3 element (-214/-190) in the -215 promoter and deletion of this element (-171 promoter) blunted type I downregulation with DEN. In contrast, betae3 mutation in the -408 promoters was not effective in attenuating the DEN response, suggesting the existence of additional DEN-responsive sites between -408 and -215. Western blotting and gel mobility supershift assays demonstrated decreased expression and DNA binding of transcription enhancer factor 1 (TEF-1) with DEN, suggesting that this decrease may contribute to type I MHC downregulation in denervated muscle.

Regulation of the S100B gene by alpha 1-adrenergic stimulation in cardiac myocytes

We previously reported that S100B, a 20-kDa Ca(2+)-binding homodimer, inhibited the postinfarct myocardial hypertrophic response mediated by alpha(1)-adrenergic stimulation through the protein kinase C (PKC) signaling pathway. In the present study, we examined whether the same pathway induced the S100B gene, supporting the hypothesis that S100B is a feedback negative regulator of this pathway. We transfected cultured neonatal rat cardiac myocytes with a luciferase reporter gene driven by the maximal human S100B promoter and progressively shorter segments of this promoter sequentially deleted from the 5' end. We identified a basic promoter essential for transcription spanning 162 bp upstream of the transcription initiation site and positive (at -782/-162 and -6,689/-4,463) and negative (at -4,463/-782) myocyte-selective regulatory elements. We showed that the basic and maximal S100B promoters were activated specifically by alpha(1)-adrenergic agonists through the alpha(1A)-adrenergic receptor, but not by any other trophic hormonal stimuli. The activation of the S100B promoter was mediated through the PKC signaling pathway. Transcription enhancer factor-1 (TEF-1) and related to TEF-1 (RTEF-1) influenced transcription from the maximal, but not the basic, promoter implicating active MCAT elements upstream from the basic promoter. Acting in opposing fashions, TEF-1 transrepressed the S100B promoter and RTEF-1 transactivated the promoter. Our results suggest that alpha(1)-adrenergic stimulation induces the S100B gene after myocardial infarction through the PKC signaling pathway and that this induction is modulated by TEF-1 and RTEF-1.

Mammalian vestigial-like 2, a cofactor of TEF-1 and MEF2 transcription factors that promotes skeletal muscle differentiation

Expression of many skeletal muscle-specific genes depends on TEF-1 (transcription enhancer factor-1) and MEF2 transcription factors. In Drosophila, the TEF-1 homolog Scalloped interacts with the cofactor Vestigial to drive differentiation of the wing and indirect flight muscles. Here, we identify three mammalian vestigial-like genes, Vgl-1, Vgl-2, and Vgl-3, that share homology in a TEF-1 interaction domain. Vgl-1 and Vgl-3 transcripts are enriched in the placenta, whereas Vgl-2 is expressed in the differentiating somites and branchial arches during embryogenesis and is skeletal muscle-specific in the adult. During muscle differentiation, Vgl-2 mRNA levels increase and Vgl-2 protein translocates from the cytoplasm to the nucleus. In situ hybridization revealed co-expression of Vgl-2 with myogenin in the differentiating muscle of embryonic myotomes but not in newly formed somites prior to muscle differentiation. Like Vgl-1, Vgl-2 interacts with TEF-1. In addition, we show that Vgl-2 interacts with MEF2 in a mammalian two-hybrid assay and that Vgl-2 selectively binds to MEF2 in vitro. Co-expression of Vgl-2 with MEF2 markedly co-activates an MEF2-dependent promoter through its MEF2 element. Overexpression of Vgl-2 in MyoD-transfected 10T(1/2) cells markedly increased myosin heavy chain expression, a marker of terminal muscle differentiation. These results identify Vgl-2 as an important new component of the myogenic program.

TEF-1 transcription factors regulate activity of the mouse mammary tumor virus LTR

The mouse mammary tumor virus long terminal repeat (LTR) is a potent transcriptional enhancer. We identified several putative binding sites for the TEF-1 family of transcription factors (TEF-1, RTEF-1, DTEF-1, and ETF) in the proximal negative regulatory element of the LTR. Gel mobility shift assays revealed strong TEF-1 factor binding to one site using nuclear extracts from CV-1 cells and from the human breast cancer cell line MCF-7. Mutation of this site increased basal activity of the LTR. In transient transfection assays, TEF-1 squelched the basal LTR activity and completely abrogated the response to the glucocorticoid dexamethasone. RTEF-1 and DTEF-1 had little effect on the basal activity, whereas ETF activated the LTR. These TEF-1 factors also interfered with the response to dexamethasone. Taken together, our results reveal an important new role for TEF-1 factors in regulating MMTV LTR activity and suggest that TEF-1 factors might participate in mammary tumorigenesis.

Alpha(1)-adrenergic activation of the cardiac ankyrin repeat protein gene in cardiac myocytes

Cardiac ankyrin repeat protein (CARP) is a nuclear transcription cofactor that is activated by multiple signaling pathways in hypertrophic cardiac myocytes. Since CARP has been reported to be a transcriptional co-repressor, its activation during hypertrophy might contribute to the deregulation of gene expression leading to heart failure. Here, we found that alpha(1)-adrenergic signaling activates CARP mRNA expression in rat cardiac myocytes. To examine how alpha(1)-adrenergic signaling activates the CARP gene, a 660 bp fragment of the mouse CARP promoter was cloned. Previous reports suggested that the mouse CARP promoter was dependent on the GATA4 transcription factor whereas the human CARP promoter was dependent on transcriptional enhancer factor-1 (TEF-1). TEF-1 and GATA4 transcription factors, known mediators of alpha(1)-adrenergic signaling, bound to the mouse CARP promoter at several sites as determined by gel mobility shift assays. These sites are highly conserved between the mouse and human promoters, suggesting that they are functionally important in both. Mutation analysis showed that binding of TEF-1 factors is required for basal activity of the CARP promoter in cardiac myocytes. However, over-expression of TEF-1 factors could not potentiate the response of the CARP promoter to alpha(1)-adrenergic stimulation. On the other hand, the alpha(1)-adrenergic response was potentiated by GATA4 over-expression. Taken together, our results demonstrate that alpha(1)-adrenergic signaling regulates CARP expression in cardiac myocytes, in part through the transcription factor GATA4.

Mouse DTEF-1 (ETFR-1, TEF-5) is a transcriptional activator in alpha 1-adrenergic agonist-stimulated cardiac myocytes

alpha(1)-Adrenergic signaling in cardiac myocytes activates the skeletal muscle alpha-actin gene through an MCAT cis-element, the binding site of the transcriptional enhancer factor-1 (TEF-1) family of transcription factors. TEF-1 accounts for more than 85% of the MCAT binding activity in neonatal rat cardiac myocytes. Other TEF-1 family members account for the rest. Although TEF-1 itself has little effect on the alpha(1)-adrenergic activation of skeletal muscle alpha-actin, the related factor RTEF-1 augments the response and is a target of alpha(1)-adrenergic signaling. Here, we examined another TEF-1 family member expressed in cardiac muscle, DTEF-1, and observed that it also augmented the alpha(1)-adrenergic response of skeletal muscle alpha-actin. A DTEF-1 peptide-specific antibody revealed that endogenous DTEF-1 accounts for up to 5% of the MCAT binding activity in neonatal rat cardiac myocytes. A TEF-1/DTEF-1 chimera suggests that alpha(1)-adrenergic signaling modulates DTEF-1 function. Orthophosphate labeling and immunoprecipitation of an epitope-tagged DTEF-1 showed that DTEF-1 is phosphorylated in vivo. alpha(1)-Adrenergic stimulation increased while phosphatase treatment lowered the MCAT binding by DTEF-1 and the endogenous non-TEF-1 MCAT-binding factor. In contrast, alpha(1)-adrenergic stimulation did not alter, and phosphatase treatment increased, MCAT binding of TEF-1 and RTEF-1. Taken together, these results suggest that DTEF-1 is a target for alpha(1)-adrenergic activation of the skeletal muscle alpha-actin gene in neonatal rat cardiac myocytes.

TEF-1 and MEF2 transcription factors interact to regulate muscle-specific promoters

Many muscle-specific genes are regulated by transcriptional enhancer factor-1 (TEF-1), serum response factor (SRF), and myocyte enhancer factor-2 (MEF2) transcription factors. TEF-1 interacts with the MADS domain of SRF and together SRF and TEF-1 co-activate the skeletal alpha-actin promoter. MEF2 factors also contain a MADS domain with 50% amino acid identity to the SRF MADS domain. Because of this sequence divergence, some SRF co-factors do not interact with MEF2. To demonstrate that TEF-1 factors could also interact with MEF2 through its MADS domain, we used co-immunoprecipitation and GST pull-down assays in vitro and a mammalian two-hybrid assay in vivo. The MADS domain was not sufficient for MEF2 interaction with TEF-1, because additional sequences in the activation domains of both proteins were required for in vivo association. The physiological significance of this interaction was also demonstrated by transient transfection assays using muscle-specific promoters. Our results suggest that by their interaction with MEF2 factors, TEF-1 factors can control MEF2-dependent muscle-specific gene expression.

Functional overload increases beta-MHC promoter activity in rodent fast muscle via the proximal MCAT (betae3) site

Functional overload (OL) of the rat plantaris muscle by the removal of synergistic muscles induces a shift in the myosin heavy chain (MHC) isoform expression profile from the fast isoforms toward the slow type I, or, beta-MHC isoform. Different length rat beta-MHC promoters were linked to a firefly luciferase reporter gene and injected in control and OL plantaris muscles. Reporter activities of -3,500, -914, -408, and -215 bp promoters increased in response to 1 wk of OL. The smallest -171 bp promoter was not responsive to OL. Mutation analyses of putative regulatory elements within the -171 and -408 bp region were performed. The -408 bp promoters containing mutations of the betae1, distal muscle CAT (MCAT; betae2), CACC, or A/T-rich (GATA), were still responsive to OL. Only the proximal MCAT (betae3) mutation abolished the OL response. Gel mobility shift assays revealed a significantly higher level of complex formation of the betae3 probe with nuclear protein from OL plantaris compared with control plantaris. These results suggest that the betae3 site functions as a putative OL-responsive element in the rat beta-MHC gene promoter.

Transcriptional regulation of the type I myosin heavy chain promoter in inactive rat soleus

Chronic muscle inactivity with spinal cord isolation (SI) decreases expression of slow type I myosin heavy chain (MHC) while increasing expression of the faster MHC isoforms, primarily IIx. The purpose of this study was to determine whether type I MHC downregulation in the soleus muscle of SI rats is regulated transcriptionally and to identify cis-acting elements or regions of the rat type I MHC gene promoter involved in this response. One week of SI significantly decreased in vivo activity of the -3500-, -408-, -299-, -215-, and -171-bp type I MHC promoters. The activity of all tested deletions of the type I MHC promoter, relative to the human skeletal alpha-actin promoter, were significantly reduced in the SI soleus, except activity of the -171-bp promoter, which increased. Mutation of the betae3 element (-214/-190 bp) in the -215- and -408-bp promoters and deletion of this element (-171-bp promoter) attenuated type I downregulation with SI. Gel mobility shift assays demonstrated a decrease in transcription enhancer factor-1 binding to the betae3 element with SI, despite an increase in total binding to this region. These results demonstrate that type I MHC downregulation with SI is transcriptionally regulated and suggest that interactions between transcription enhancer factor-1 and the betae3 element are likely involved in this response.

Cloning and characterization of the mouse alpha1C/A-adrenergic receptor gene and analysis of an alpha1C promoter in cardiac myocytes: role of an MCAT element that binds transcriptional enhancer factor-1 (TEF-1)

alpha1-Adrenergic receptor (AR) subtypes in the heart are expressed by myocytes but not by fibroblasts, a feature that distinguishes alpha1-ARs from beta-ARs. Here we studied myocyte-specific expression of alpha1-ARs, focusing on the subtype alpha1C (also called alpha1A), a subtype implicated in cardiac hypertrophic signaling in rat models. We first cloned the mouse alpha1C-AR gene, which consisted of two exons with an 18 kb intron, similar to the alpha1B-AR gene. The receptor coding sequence was >90% homologous to that of rat and human. alpha1C-AR transcription in mouse heart was initiated from a single Inr consensus sequence at -588 from the ATG; this and a putative polyadenylation sequence 8.5 kb 3' could account for the predominant 11 kb alpha1C mRNA in mouse heart. A 5'-nontranscribed fragment of 4.4 kb was active as a promoter in cardiac myocytes but not in fibroblasts. Promoter activity in myocytes required a single muscle CAT (MCAT) element, and this MCAT bound in vitro to recombinant and endogenous transcriptional enhancer factor-1. Thus, alpha1C-AR transcription in cardiac myocytes shares MCAT dependence with other cardiac-specific genes, including the alpha- and beta-myosin heavy chains, skeletal alpha-actin, and brain natriuretic peptide. However, the mouse alpha1C gene was not transcribed in the neonatal heart and was not activated by alpha1-AR and other hypertrophic agonists in rat myocytes, and thus differed from other MCAT-dependent genes and the rat alpha1C gene.

Physical interaction between the MADS box of serum response factor and the TEA/ATTS DNA-binding domain of transcription enhancer factor-1

Serum response factor is a MADS box transcription factor that binds to consensus sequences CC(A/T)(6)GG found in the promoter region of several serum-inducible and muscle-specific genes. In skeletal myocytes serum response factor (SRF) has been shown to heterodimerize with the myogenic basic helix-loop-helix family of factors, related to MyoD, for control of muscle gene regulation. Here we report that SRF binds to another myogenic factor, TEF-1, that has been implicated in the regulation of a variety of cardiac muscle genes. By using different biochemical assays such as affinity precipitation of protein, GST-pulldown assay, and coimmunoprecipitation of proteins, we show that SRF binds to TEF-1 both in in vitro and in vivo assay conditions. A strong interaction of SRF with TEF-1 was seen even when one protein was denatured and immobilized on nitrocellulose membrane, indicating a direct and stable interaction between SRF and TEF-1, which occurs without a cofactor. This interaction is mediated through the C-terminal subdomain of MADS box of SRF encompassing amino acids 204-244 and the putative 2nd and 3rd alpha-helix/beta-sheet configuration of the TEA/ATTS DNA-binding domain of TEF-1. In the transient transfection assay, a positive cooperative effect of SRF and TEF-1 was observed when DNA-binding sites for both factors, serum response element and M-CAT respectively, were intact; mutation of either site abolished their synergistic effect. Similarly, an SRF mutant, SRFpm-1, defective in DNA binding failed to collaborate with TEF-1 for gene regulation, indicating that the synergistic trans-activation function of SRF and TEF-1 occurs via their binding to cognate DNA-binding sites. Our results demonstrate a novel association between SRF and TEF-1 for cardiac muscle gene regulation and disclose a general mechanism by which these two super families of factors are likely to control diversified biological functions.

Transcriptional regulation and function during the human cell cycle

We report here the transcriptional profiling of the cell cycle on a genome-wide scale in human fibroblasts. We identified approximately 700 genes that display transcriptional fluctuation with a periodicity consistent with that of the cell cycle. Systematic analysis of these genes revealed functional organization within groups of coregulated transcripts. A diverse set of cytoskeletal reorganization genes exhibit cell-cycle-dependent regulation, indicating that biological pathways are redirected for the execution of cell division. Many genes involved in cell motility and remodeling of the extracellular matrix are expressed predominantly in M phase, indicating a mechanism for balancing proliferative and invasive cellular behavior. Transcripts upregulated during S phase displayed extensive overlap with genes induced by DNA damage; cell-cycle-regulated transcripts may therefore constitute coherent programs used in response to external stimuli. Our data also provide clues to biological function for hundreds of previously uncharacterized human genes.

Alpha 1-adrenergic receptor regulation: basic science and clinical implications

Adrenergic receptors (ARs) are members of the G-protein-coupled receptor family, which includes alpha 1ARs, alpha 2ARs, beta 1ARs, beta 2ARs, beta 3ARs, adenosine, muscarinic, angiotensin, endothelin receptors, and many others that are responsible for a large variety of physiologic effects through G-protein coupling. This review focuses on alpha 1ARs and their regulation at both the mRNA and protein levels. Currently, three alpha 1AR subtypes have been characterized both pharmacologically and at the gene level: alpha 1aAR, alpha 1bAR, and alpha 1dAR. These are expressed in a species- and tissue-dependent manner. Mutagenesis approaches have been extremely valuable in the identification of key residues that govern alpha 1AR ligand binding and signaling. These studies reveal that alpha 1ARs have evolved an exquisitely sensitive regulation of their activity in which any disruption of the native structure has profound effects on subsequent function and effector coupling. Significant advances have also been made in the elucidation of signaling pathway components, resulting in the identification of novel pathways that can lead to pathologic conditions. Specific topics include mitogen-activated protein kinase, phosphatidylinositol 3-kinase, and G-protein-coupled receptor cross-talk pathways. Within this context, recent studies identifying underlying transcriptional mechanisms involved in the regulation of the alpha 1AR subtypes are also discussed. Finally, given the potentially important role of alpha 1ARs in the vasculature, as well as in the pathology of many diseases, such as myocardial hypertrophy and benign prostatic hyperplasia, the clinical relevance of alpha 1AR distribution, pharmacology, and therapeutic intervention is reviewed.

Genetic dissection of cardiac growth control pathways

Cardiac muscle cells exhibit two related but distinct modes of growth that are highly regulated during development and disease. Cardiac myocytes rapidly proliferate during fetal life but exit the cell cycle irreversibly soon after birth, following which the predominant form of growth shifts from hyperplastic to hypertrophic. Much research has focused on identifying the candidate mitogens, hypertrophic agonists, and signaling pathways that mediate these processes in isolated cells. What drives the proliferative growth of embryonic myocardium in vivo and the mechanisms by which adult cardiac myocytes hypertrophy in vivo are less clear. Efforts to answer these questions have benefited from rapid progress made in techniques to manipulate the murine genome. Complementary technologies for gain- and loss-of-function now permit a mutational analysis of these growth control pathways in vivo in the intact heart. These studies have confirmed the importance of suspected pathways, have implicated unexpected pathways as well, and have led to new paradigms for the control of cardiac growth.