Transcriptional enhancer factor-1 in cardiac myocytes interacts with an alpha 1-adrenergic- and beta-protein kinase C-inducible element in the rat beta-myosin heavy chain promoter

Divergence of beta-myosin heavy chain (betaMHC) expression in fetal rat cardiomyocytes in vitro and adult rat heart in vivo

The myosin heavy chain gene products are an important determinant of myocardial functional properties. Although a strong positive element (beta f1) within the betaMHC promoter region has previously been identified, to date no species comparisons in promoter strength have been made. To examine this question, we have used betaMHC deletion constructs, containing the rat or human beta f1 enhancer region, to determine expression both in vitro using rat fetal cardiomyocytes and in vivo by direct injection into adult rat heart. When reporter constructs were transfected into cultured fetal rat cardiomyocytes, the human beta reporter was expressed more than 3 fold above the equivalent rat construct. Exchange of the beta f1 enhancer indicated that the human sequence of the beta f1 enhancer was largely responsible. However, these findings were not replicated when the reporters were injected into the adult rat heart. In the adult myocardium the levels of reporter expression were similar for the betaMHC promoter reporters studied. These findings demonstrate a divergence between primary cardiomyocytes maintained in culture and the cardiomyocytes found within the intact adult heart.

The mammalian myosin heavy chain gene family

Myosin is a highly conserved, ubiquitous protein found in all eukaryotic cells, where it provides the motor function for diverse movements such as cytokinesis, phagocytosis, and muscle contraction. All myosins contain an amino-terminal motor/head domain and a carboxy-terminal tail domain. Due to the extensive number of different molecules identified to date, myosins have been divided into seven distinct classes based on the properties of the head domain. One such class, class II myosins, consists of the conventional two-headed myosins that form filaments and are composed of two myosin heavy chain (MYH) subunits and four myosin light chain subunits. The MYH subunit contains the ATPase activity providing energy that is the driving force for contractile processes mentioned above, and numerous MYH isoforms exist in vertebrates to carry out this function. The MYHs involved in striated muscle contraction in mammals are the focus of the current review. The genetics, molecular biology, and biochemical properties of mammalian MYHs are discussed below. MYH gene expression patterns in developing and adult striated muscles are described in detail, as are studies of regulation of MYH genes in the heart. The discovery that mutant MYH isoforms have a causal role in the human disease familial hypertrophic cardiomyopathy (FHC) has implemented structure/function investigations of MYHs. The regulation of MYH genes expressed in skeletal muscle and the potential functional implications that distinct MYH isoforms may have on muscle physiology are addressed.

Repression of transcriptional enhancer factor-1 and activator protein-1-dependent enhancer activity by vascular actin single-stranded DNA binding factor 2

Transcriptional repression of the murine vascular smooth muscle alpha-actin gene in fibroblasts results from the interaction of two sequence-specific single-stranded DNA binding activities (VACssBF1 and VACssBF2) with opposite strands of an essential transcriptional enhancer factor-1 (TEF-1) element (Sun, S., Stoflet, E. S., Cogan, J. G., Strauch, A. R., and Getz, M. J. (1995) Mol. Cell. Biol. 15, 2429-2436). Here, we identify a sequence element located within a protein-coding exon of the gene that bears structural similarity with the TEF-1 enhancer. This includes a 30-base pair region of purine-pyrimidine asymmetry encompassing a perfect 6-base pair GGAATG TEF-1 recognition motif. Unlike the enhancer, however, the exon sequence exhibits no TEF-1 binding activity nor does the pyrimidine-rich strand bind VACssBF1. However, VACssBF2 interacts equally well with the purine-rich strand of both the enhancer and the exon sequence. To test the ability of VACssBF2 to independently repress transcription, the exon sequence was placed upstream of a deletionally activated promoter containing an intact TEF-1 binding site. The exon sequence repressed promoter activity, whereas a mutant deficient in VACssBF2 binding did not. Moreover, VACssBF2 similarly repressed activator protein-1-dependent transcription of a heterologous tissue factor promoter. These results suggest that VACssBF2 possesses an intrinsic ability to disrupt enhancer function independently of the enhancer-binding proteins involved.

A novel family of developmentally regulated mammalian transcription factors containing the TEA/ATTS DNA binding domain

We describe the molecular cloning of two novel human and murine transcription factors containing the TEA/ATTS DNA binding domain and related to transcriptional enhancer factor-1 (TEF-1). These factors bind to the consensus TEA/ATTS cognate binding site exemplified by the GT-IIC and Sph enhansons of the SV40 enhancer but differ in their ability to bind cooperatively to tandemly repeated sites. The human TEFs are differentially expressed in cultured cell lines and the mouse (m)TEFs are differentially expressed in embryonic and extra-embryonic tissues in early post-implantation embryos. Strikingly, at later stages of embryogenesis, mTEF-3 is specifically expressed in skeletal muscle precursors, whereas mTEF-1 is expressed not only in developing skeletal muscle but also in the myocardium. Together with previous data, these results point to important, partially redundant, roles for these TEF proteins in myogenesis and cardiogenesis. In addition, mTEF-1 is strongly coexpressed with mTEF-4 in mitotic neuroblasts, while accentuated mTEF-4 expression is also observed in the gut and the nephrogenic region of the kidney. These observations suggest additional roles for the TEF proteins in central nervous system development and organogenesis.

Interleukin-1beta is a negative transcriptional regulator of alpha1-adrenergic induced gene expression in cultured cardiac myocytes

We recently reported that interleukin-1beta (IL-1beta) induces a novel form of cardiac myocyte hypertrophy characterized by an increase in protein content but an absence of the fetal program of skeletal alpha-actin or beta-myosin heavy chain (beta-MHC) gene expression (Palmer, J. N., Hartogensis, W. E., Patten, M., Fortuin, F. D., and Long, C. S. (1995) J. Clin. Invest. 95, 2555-2564). Because of the apparent disparity between this myocardial phenotype and that seen with other hypertrophic agents in culture, such as catecholamines, we investigated the effect of IL-1beta on alpha1-induced cardiomyocyte hypertrophy. Although there was no augmentation in total protein when IL-1beta and phenylephrine were given simultaneously, IL-1beta attenuated the increase in contractile protein mRNAs (skeletal alpha-actin and beta-MHC) in response to phenylephrine. Transient transfection studies with skeletal alpha-actin and beta-MHC promoter constructs linked to the chloramphenicol acetyltransferase (CAT)-reporter gene indicate that repression occurred at the level of gene transcription. In view of the previously reported activity of the zinc finger protein YY1 in the negative regulation of the skeletal alpha-actin promoter in cardiomyocytes (MacLellan, W. R., Lee, T. C., Schwartz, R. J., and Schneider, M. D. (1994) J. Biol. Chem. 269, 16754-16760), we investigated the potential role of this factor in the IL-1beta-mediated effects. Using transient transfection, we found that a mutation in the YY1 binding site of the skeletal alpha-actin promoter abolished the inhibitory effect of IL-1beta. We further found that the 127-base pair fragment of the skeletal alpha-actin promoter required for the IL-1beta effect is also required for inhibition by the overexpression of YY1 in the myocytes. Furthermore, increased levels of YY1 protein are found in IL-1beta treated myocytes. Taken together these results suggest that the repression of contractile protein gene transcription by IL-1beta may be due, at least in part, to activation of the negative transcription factor YY1.

TEF-1 transrepression in BeWo cells is mediated through interactions with the TATA-binding protein, TBP

Transcription enhancer factor-1 (TEF-1) has been implicated in transactivating a placental enhancer (CSEn) that regulates human chorionic somatomammotropin (hCS) gene activity. We demonstrated that TEF-1 represses hCS promoter activity in choriocarcinoma (BeWo) cells (Jiang, S.W., and Eberhardt, N.L. (1995) J. Biol. Chem. 270, 13609-13915), suggesting that TEF-1 interacts with basal transcription factors. Here we demonstrate that hTEF-1 overexpression inhibits minimal hCS promoters containing TATA and/or initiator elements, Rous sarcoma virus and thymidine kinase promoters in BeWo cells. Cotransfection of TEF-1 antisense oligonucleotides alleviated exogenous TEF-1-mediated repression and increased basal hCS promoter activity, indicating that endogenous TEF-1 exerts repressor activity. GST-TEF-1 fusion peptides fixed to glutathione-Sepharose beads retained in vitro-generated human TATA-binding protein, hTBP. The TEF-1 proline-rich domain was essential for TBP binding, but polypeptides also containing the zinc finger domain bound TBP with higher apparent affinity. TBP supershifted hTEF-GT-IIC DNA complexes, but TEF-1 inhibited in vitro binding of TBP to the TATA motif. Coexpression of TBP and TEF-1 in BeWo cells alleviated TEF-1-mediated transrepression, indicating that the TBP-TEF-1 interaction is functional in vivo. The data indicate that TEF-1 transrepression is mediated by direct interactions with TBP, possibly by inhibiting preinitiation complex formation.

DTEF-1, a novel member of the transcription enhancer factor-1 (TEF-1) multigene family

M-CAT motifs mediate muscle-specific transcriptional activity via interaction with binding factors that are antigenically and biochemically related to vertebrate transcription enhancer factor-1 (TEF-1), a member of the TEA/ATTS domain family of transcription factors. M-CAT binding activities present in cardiac and skeletal muscle tissues cannot be fully accounted for by existing cloned isoforms of TEF-1. TEF-1-related cDNAs isolated from heart libraries indicate that at least three classes of TEF-1-related cDNAs are expressed in these and other tissues. One class are homologues of the human TEF-1 originally cloned from HeLa cells (Xiao, J. H., Davidson, I., Matthes, H., Garnier, J. M., and Chambon, P. (1991) Cell 65, 551-568). A second class represents homologues of the avian TEF-1-related gene previously isolated (Stewart, A. F., Larkin, S. B., Farrance, I. K., Mar, J. H., Hall, D. E., and Ordahl, C. P. (1994) J. Biol. Chem. 269, 3147-3150). The third class consists of a novel, divergent TEF-1 cDNA, named DTEF-1, and its preliminary characterization is described here. Two isoforms of DTEF-1 (DTEF-1A and DTEF-1B) were isolated as 1.9-kilobase pair clones with putative open reading frames of 433 and 432 amino acids whose differences are attributable to alternative splicing at the C terminus of the TEA DNA binding domain. Cardiac muscle contains high levels of DTEF-1 transcripts, but unexpectedly low levels are detected in skeletal muscle. DTEF-1 transcripts are present at intermediate levels in gizzard and lung, and at low levels in kidney. DTEF-1A is a sequence-specific M-CAT-binding factor. The distinct spatial pattern of expression, and unusual amino acid sequence in its DNA binding domain, may indicate a particular role for DTEF-1 in cell-specific gene regulation. Recent work also suggests that at least one more TEF-1-related gene exists in vertebrates. We propose a naming system for the four TEF-1 gene family members identified to date that preserves existing nomenclature and provides a means for extending that nomenclature as additional family members may be identified.

The role of transcription enhancer factor-1 (TEF-1) related proteins in the formation of M-CAT binding complexes in muscle and non-muscle tissues

M-CAT sites are required for the activity of many promoters in cardiac and skeletal muscle. M-CAT binding activity is muscle-enriched, but is found in many tissues and is immunologically related to the HeLa transcription enhancer factor-1 (TEF-1). TEF-1-related cDNAs (RTEF-1) have been cloned from chick heart. RTEF-1 mRNA is muscle-enriched, consistent with a role for RTEF-1 in the regulation of muscle-specific gene expression. Here, we have examined the tissue distribution of TEF-1-related proteins and of M-CAT binding activity by Western analysis and mobility shift polyacrylamide gel electrophoresis. TEF-1-related proteins of 57, 54 and 52 kDa were found in most tissues with the highest levels in muscle tissues. All of these TEF-1-related proteins bound M-CAT DNA and the 57- and 54-kDa TEF-1-related polypeptides were phosphorylated. Proteolytic digestion mapping showed that the 54-kDa TEF-1-related polypeptide is encoded by a different gene than the 52- and 57-kDa TEF-1-related polypeptides. A comparison of the migration and proteolytic digestion of the 54-kDa TEF-1-related polypeptide with proteins encoded by the cloned RTEF-1 cDNAs showed that the 54-kDa TEF-1-related polypeptide is encoded by RTEF-1A. High resolution mobility shift polyacrylamide gel electrophoresis showed multiple M-CAT binding activities in tissues. All of these activities contained TEF-1-related proteins. One protein-M-CAT DNA complex was muscle-enriched and was up-regulated upon differentiation of a skeletal muscle cell line. This complex contained the 54-kDa TEF-1-related polypeptide. Therefore, RTEF1-A protein is a component of a muscle-enriched transcription complex that forms on M-CAT sites and may play a key role in the regulation of transcription in muscle.

Alpha1-adrenergic receptor subtype mRNAs are differentially regulated by alpha1-adrenergic and other hypertrophic stimuli in cardiac myocytes in culture and in vivo. Repression of alpha1B and alpha1D but induction of alpha1C

The three cloned alpha1-adrenergic receptor (AR) subtypes, alpha1B, alpha1C, and alpha1D, can all couple to the same effector, phospholipase C, and the reason(s) for conservation of multiple subtypes remain uncertain. All three alpha1-ARs are expressed natively in cultured neonatal rat cardiac myocytes, where chronic exposure to the agonist catecholamine norepinephrine (NE) induces hypertrophic growth and gene transcription. We show here, using RNase protection, that the alpha1-AR subtype mRNAs respond in distinctly different ways during prolonged NE exposure (12 72 h). Alpha1B and alpha1D mRNA levels were repressed by NE, whereas alpha1C mRNA was induced. Changes in mRNA levels were mediated by an alpha1-AR, were not explained by altered mRNA stability, and were reflected in receptor proteins by [3H]prazosin binding. alpha1-AR-stimulated phosphoinositide hydrolysis and myocyte growth were not desensitized. Three other hypertrophic agonists in culture, endothelin-1, PGF2alpha, and phorbol 12-myristate 13-acetate, also induced alpha1C mRNA and repressed alpha1B mRNA. In myocytes from hearts with pressure overload hypertrophy, alpha1 mRNA changes were identical to those produced by NE in culture. These results provide the first example of a difference in regulation among alpha1-AR subtypes expressed natively in the same cell. Transcriptional induction of the alpha1C-AR could be a mechanism for sustained growth signaling through this receptor and is a common feature of a hypertrophic phenotype in cardiac myocytes.

Mouse mutants and cardiac development: new molecular insights into cardiogenesis

Understanding the genetic control of cardiac development has been greatly assisted by the newly acquired ability to generate targeted mutations in the mouse. A number of mutations in genes that directly or indirectly affect cardiac development have now been reported, and the phenotypes of these mutations have suggested that cardiac development is under complex genetic control. Further analysis of the mouse model system should help elucidate the etiology of human congenital cardiovascular anomalies.

cDNA cloning and characterization of murine transcriptional enhancer factor-1-related protein 1, a transcription factor that binds to the M-CAT motif

The M-CAT motif is a cis-regulatory DNA sequence that is essential for muscle-specific transcription of several genes. Previously, we had shown that both muscle-specific (A1) and ubiquitous (A2) factors bind to an essential M-CAT motif in the myosin heavy chain beta gene and that the ubiquitous factor is transcriptional enhancer factor (TEF)-1. Here we report the isolation of mouse cDNAs encoding two forms (a and b) of a TEF-1-related protein, TEFR1. The TEFR1a cDNA encodes a 427-amino acid protein. The coding region of TEFR1b is identical to 1a in both nucleotide and predicted amino acid sequence except for the absence of 43 amino acids downstream of the TEA DNA-binding domain. Three TEFR1 transcripts (approximately 7, approximately 3.5, and approximately 2 kilobase pairs) are enriched in differentiated skeletal muscle (myotubes) relative to undifferentiated skeletal muscle (myoblasts) and non-muscle cells in culture. In situ hybridization analysis indicated that TEFR1 transcripts are enriched in the skeletal muscle lineage during mouse embryogenesis. Transient expression of fusion proteins of TEFR1 and the yeast GAL4 DNA-binding domain in cell lines activated the expression of chloramphenicol acetyltransferase (CAT) reporter constructs containing GAL4 binding sites, indicating that TEFR1 contains an activation domain. An anti-TEFR1 polyclonal antibody supershifted the muscle-specific M-CAT.A1 factor complex in gel mobility shift assays, suggesting that TEFR1 is a major component of this complex. Our results suggest that TEFR1 might play a role in the embryonic development of skeletal muscle in the mouse.

Control of beta-myosin heavy chain expression in systemic hypertension and caloric restriction in the rat heart

In the rat left ventricle, both pressure overload induced by abdominal aortic constriction (Abcon) and caloric restriction (CR) induce an increase in the steady-state level of the beta-myosin heavy chain (MHC) protein and mRNA. Both models also induce a concomitant decrease in the alpha-MHC protein and mRNA. The goals of this study were to 1) determine if the changes in MHC expression in the models are due to altered transcription and 2) identify the relative levels of some key factors interacting with the regulatory regions of these genes. Female Sprague-Dawley rats were randomly assigned to the following groups: 1) normal control (NC), 2) Abcon, and 3) CR. After 5 wk of experimental manipulations, myocardial nuclei were isolated. These nuclei were used for 1) nuclear run-on assays or 2) nuclear extract, which was prepared and used for gel mobility shift assays (GMSAs). Nuclear run-on assays demonstrated that the increase in beta-MHC mRNA and protein expression in both Abcon and CR can be at least partially attributed to increased transcription. The concomitant decrease in alpha-MHC content can similarly be attributed to a decrease in transcription of this gene. Furthermore, GMSAs demonstrate that nuclear extract from each group interact differently with certain elements known to be important for expression in vitro. CR nuclear extracts have a 25.6 +/- 7.2% decrease (P < 0.05 vs. NC) in interaction with a thyroid-responsive element, a potential repressor of beta-MHC transcription.(ABSTRACT TRUNCATED AT 250 WORDS)

The alpha 1C-adrenoceptor in human prostate: cloning, functional expression, and localization to specific prostatic cell types

1. Benign prostatic hyperplasia (BPH) causes urinary obstruction in aging men that frequently requires surgery to relieve the symptoms of urinary retention, nocturia, and micturition. Smooth muscle tone which contributes to the urethral constriction in the enlarged gland appears to be mediated by the alpha 1-adrenoceptors. In this paper, molecular and pharmacological approaches are used to establish the role played by the alpha 1C-adrenoceptor subtype in the prostate. 2. The alpha 1-adrenoceptor subtype(s) expressed in human prostate were investigated by use of polymerase chain reaction (PCR), Northern blot, and in situ hybridization. The alpha 1C subtype was found in both prostate stromal and glandular cells while alpha 1B and alpha 1D subtypes were expressed in glandular cells. High expression levels for alpha 1C were observed in prostate cancer tissues in both stroma and glandular cells. 3. Full length alpha 1C-adrenoceptor cDNA was cloned from human prostate. Stable mammalian cell lines expressing human alpha 1B-, alpha 1C-, and alpha 1D-adrenoceptors were made. Membranes prepared from these cell lines and human prostate were used to evaluate the pharmacological profiles of human alpha 1B-, alpha 1C- and alpha 1D-adrenoceptors in comparison to human prostate. Leverage plot analysis of compound affinities determined by competition for [125I]-I-HEAT binding demonstrated that the alpha 1C subtype is the predominant alpha 1-adrenoceptor in human prostate. 4. The alpha 1-adrenoceptors cause smooth muscle constriction by coupling to IP3 turnover and intracellular Ca2+ release. Using stable cell lines to measure IP3 production in response to noradrenaline, alpha 1C stimulated IP3 production most efficiently, with alpha 1B at an intermediate level, while little IP3 above background could be detected with alpha 1D. These results supported a functional role of the alpha 1C-adrenoceptor on prostate smooth muscle constriction by noradrenaline stimulation.

Involvement of a protein distinct from transcription enhancer factor-1 (TEF-1) in mediating human chorionic somatomammotropin gene enhancer function through the GT-IIC enhanson in choriocarcinoma and COS cells

Previous studies suggested that transcription enhancer factor-1 (TEF-1) was involved in mediating the human chorionic somatomammotropin (hCS) gene enhancer (CSEn) function (Jiang, S.-W., and Eberhardt, N. L. (1994) J. Biol. Chem. 269, 10384-10392). We now show that an unrelated protein (CSEF-1) found in BeWo and COS-1 cells binds to the GT-IIC enhanson in CSEn and is correlated with CSEn activity in these cells. TEF-1 and CSEF-1 were distinguished by differential migration as GT-IIC complexes, thermal stability, molecular mass, and cross-reactivity with chicken TEF-1 antibodies. TEF-1 and CSEF-1 bound to the GT-IIC and Sph-I/Sph-II enhansons with identical binding properties, and in vitro generated TEF-1 competed with CSEF-1 binding to the GT-IIC motif, suggesting that their actions might be mutually exclusive. Up- and down-regulation of TEF-1 levels by expression systems and antisense oligonucleotides demonstrated that TEF-1 inhibited the hCS promoter in a manner independent of the enhancer or a known TEF-1 DNA binding site. The data suggest that TEF-1 may provide a counter-regulatory stimulus to the actions of CSEF-1, which may be involved in mediating enhancer stimulatory activity.

Plasticity of vascular smooth muscle alpha-actin gene transcription. Characterization of multiple, single-, and double-strand specific DNA-binding proteins in myoblasts and fibroblasts

Transcriptional activity of the mouse vascular smooth muscle (VSM) alpha-actin promoter was governed by both cell type and developmental stage-specific mechanisms. A purine-rich motif (PrM) located as -181 to -176 in the promoter was absolutely required for activation in mouse AKR-2B embryonic fibroblasts and partially contributed to activation in undifferentiated mouse BC3H1 myoblasts. Transcriptional enhancer factor 1 recognized the PrM and cooperated with other promoter-binding proteins to regulate serum growth factor-dependent transcription in both myoblasts and fibroblasts. Two distinct protein factors (VAC-ssBF1 and VAC-ssBF2) also were identified that bound sequence-specifically to single-stranded oligonucleotide probes that spanned both the PrM and a closely positioned negative regulatory element. VAC-ssBF1 and BF2 binding activity was detected in undifferentiated myoblasts, embryonic fibroblasts, and several smooth muscle tissues in the mouse and human. A myoblast-specific protein (VAC-RF1) also was detected that bound double-stranded probes containing a CArG-like sequence that previously was shown to impart strong, cell type specific repression. The binding activity of transcription enhancer factor 1, VAC-RF1, and VAC-ssBF1 was significantly diminished when confluent BC3H1 myoblasts differentiated into myocytes and expressed VSM alpha-actin mRNA after exposure to serum-free medium. The results indicated that cell type-specific control of the VSM alpha-actin gene promoter required the participation of multiple DNA-binding proteins, including two that were enriched in smooth muscle and had preferential affinity for single-stranded DNA.

Effects of interleukin-1 beta and nitric oxide on cardiac myocytes

Using cultured neonatal ventricular myocytes, we investigated whether nitric oxide (NO) directly influences myocyte growth. Treatment of myocytes with phenylephrine stimulated growth, as indicated by increases in atrial natriuretic factor, brain natriuretic peptide (BNP) mRNA and BNP secretion, activator protein 1 activity (activation of early-response genes), and total cellular protein content. NO was stimulated by treatment of myocytes with interleukin-1 beta (IL-1 beta) or was generated by the NO donor nitroglycerin, and its effects on total protein content and BNP secretion were measured. Treatment of cardiocytes with 3.4 nmol/L IL-1 beta for 24 hours stimulated NO (nitrite) production by threefold, which resulted from an increase in the inducible isoform of NO synthase mRNA. Dexamethasone inhibited IL-1 beta induction of nitrite production, whereas the protein kinase C inhibitor staurosporine had no effect. IL-1 beta had no effect on either basal or phenylephrine-stimulated protein content but inhibited phenylephrine-stimulated BNP secretion. Nitroglycerin (10(-7) to 10(-3) mol/L) dose-dependently increased NO production; however, only the highest dose (10(-3) mol/L) reduced basal and phenylephrine-stimulated total protein content and BNP secretion. cGMP, a second messenger of NO, had no effect on either basal or phenylephrine-stimulated BNP secretion or total protein content. In conclusion, our data indicate that BNP mRNA is stimulated by phenylephrine as shown previously for atrial natriuretic factor. Although both BNP and total protein content are increased by phenylephrine, these effects are not inhibited by NO. However, IL-1 beta inhibits phenylephrine-stimulated BNP secretion but not total protein content, suggesting that regulation of BNP secretion can be dissociated from total protein synthesis during myocyte growth.

M-CAT, CArG, and Sp1 elements are required for alpha 1-adrenergic induction of the skeletal alpha-actin promoter during cardiac myocyte hypertrophy. Transcriptional enhancer factor-1 and protein kinase C as conserved transducers of the fetal program in cardiac growth

Induction of the fetal isogenes skeletal alpha-actin (skACT) and beta-myosin heavy chain (beta-MHC) is characteristic of cardiac growth in many models, suggesting a conserved signaling pathway. However, divergent regulation has also been observed. beta-Protein kinase C (PKC) and transcriptional enhancer factor-1 (TEF-1) are involved in induction of beta-MHC in alpha 1-adrenergic-stimulated hypertrophy of cultured cardiac myocytes (Kariya, K., Farrance, I.K. G., and Simpson, P.C. (1993) J. Biol. Chem. 268, 26658-26662; Kariya, K., Karns, L. R., and Simpson, P.C. (1994) J. Biol. Chem. 269, 3775-3782). In the present study, we asked whether the skACT promoter used the same mechanism. A mouse skACT promoter fragment (-113/-46) was induced by both alpha 1-adrenergic stimulation and co-transfection of activated beta-PKC, and contained three required DNA sequence elements: M-CAT, CArG, and Sp1. The skACT M-CAT element bound TEF-1 in cardiac myocytes. Thus the skACT and beta-MHC promoters both require a TEF-1 binding site for activation by alpha 1-adrenergic stimulation, but differ in that skACT also requires a CArG box. These results provide a potential molecular basis for divergent regulation of the fetal program, and also imply that PKC and TEF-1 are conserved transducers for this program during cardiac growth.

Cloning of the rat alpha 1C-adrenergic receptor from cardiac myocytes. alpha 1C, alpha 1B, and alpha 1D mRNAs are present in cardiac myocytes but not in cardiac fibroblasts

alpha 1-Adrenergic receptor (AR) activation in cardiac muscle has several different physiological effects that might be mediated through different alpha 1-AR subtypes. Two alpha 1-AR subtypes have been cloned from the rat, the alpha 1B and the alpha 1D; both are present in adult rat heart. A third subtype, the alpha 1C, cloned from the cow and human, was reported to be absent in the rat. However, we recently found alpha 1C mRNA in adult rat heart by using a partial alpha 1C cDNA. Thus, all three cloned alpha 1-AR subtypes are present in the heart, but it is unknown whether each is expressed in cardiac myocytes or in cardiac fibroblasts. In the present study, the full-length rat alpha 1C-AR was cloned from cultured neonatal cardiac myocytes. alpha 1C mRNA transcripts of 3, 9.5, and 11 kb were present in adult rat heart by Northern blot analysis. alpha 1B-, alpha 1C-, and alpha 1D-subtype mRNAs were each present in isolated adult and neonatal cardiac myocytes by RNase protection assay. In addition, cultured neonatal cardiac myocytes expressed the three alpha 1-AR subtype mRNAs. In contrast, none of the alpha 1-AR mRNAs was detected in cultured neonatal cardiac fibroblasts. In addition, alpha 1-ARs were absent in fibroblasts by [3H]prazosin binding and norepinephrine-stimulated [3H]inositol phosphate production. The absence of alpha 1-ARs in cardiac fibroblasts differs from beta-adrenergic and angiotensin II receptors, which are present in both cardiac fibroblasts and cardiac myocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Transcriptional enhancer factor 1 disruption by a retroviral gene trap leads to heart defects and embryonic lethality in mice

We have used a retroviral gene trap in embryonic stem (ES) cells to derive a recessive embryonic lethal mouse strain, ROSA beta-geo5. Mutant embryos display an enlarged pericardial cavity, bradycardia, a dilated fourth ventricle in the brain, and die between embryonic days 11 and 12. Whereas heart development in the mutant embryos is extensive, the ventricular wall is abnormally thin with a reduced number of trabeculae. Cloning of the trapped gene indicates that proviral insertion creates a null mutation in the transcriptional enhancer factor 1 (TEF-1) gene. Although transcription of a number of muscle-specific genes believed to be TEF-1 targets appears normal, the defect in cardiogenesis is likely attributable to diminished transcription of one or several cardiac-specific genes.