A ras-dependent pathway abolishes activity of a muscle-specific enhancer upstream from the muscle creatine kinase gene.

Sternberg, E A; Spizz, Gwendolyn; Perry, M; Olson, Eric N.

doi:10.1128/mcb.9.2.594

Cited by 36 publications

(23 citation statements)

References 68 publications

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“…This finding was similar to our previous results with an H-ras-transfected myogenic derivative from the C3H1OT1/2 cell line, where even in the presence of six copies of an actively transcribed H-ras gene, the muscle phenotype was maintained and could be enhanced by 5-azacytidine treatment (18). These results suggest that increased MyoDI expression may be able to overcome a ras-mediated block to the induction of musclespecific genes (34). A recent report that a TrpE-MyoDl fusion protein specifically binds to the mck 5' enhancer (J.…”

supporting

confidence: 81%

“…Other studies have approached the question of the relationship between differentiation and transformation in muscle cells by the introduction of transforming ras genes into myoblast cell lines (18,28,34). These experiments have shown that activated N-ras or H-ras genes can prevent skeletal myoblast differentiation in some (28) but not all (18) mouse cell lines.…”

mentioning

confidence: 99%

“…These experiments have shown that activated N-ras or H-ras genes can prevent skeletal myoblast differentiation in some (28) but not all (18) mouse cell lines. Recently, Stemnberg et al (34) demonstrated that activated N-ras or H-ras expression abolished the activity of the muscle specific mck upstream enhancer and suggested that ras blocked the establishment of the myogenic phenotype by preventing the accumulation of regulatory factors required for transcriptional induction of muscle-specific genes. Here we have taken the opposite but complementary approach of introducing a determination gene into a human rhabdomyosarcoma cell line known to contain an activated N-ras gene (17).…”

mentioning

confidence: 99%

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Expression of the MyoD1 muscle determination gene defines differentiation capability but not tumorigenicity of human rhabdomyosarcomas.

et al. 1989

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Several human rhabdomyosarcoma cell lines, cultured primary tumor explants, and biopsies of tumor and normal skeletal muscle tissue expressed a 2.0-kilobase transcript that hybridized to the mouse muscle determination gene MyoD1. This transcript was found in tumor cell lines and primary explants that developed multinucleated myotubes but was absent in Wilms' tumors or cell lines and primary explants that developed multinucleated myotubes but was absent in Wilms' tumors or cell lines derived from other mesenchymal tumor cell types. Expression of the human homolog of MyoD1 therefore can define a tumor as a rhabdomyosarcoma. Transfection of the mouse MyoD1 gene into the human rhabdomyosarcoma cell line RD increased the ability of the tumor cells to differentiate into multinucleated myotubes and enhanced myosin heavy-chain gene expression but did not decrease tumorigenicity in nude mice.

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confidence: 81%

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confidence: 99%

mentioning

confidence: 99%

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Expression of the MyoD1 muscle determination gene defines differentiation capability but not tumorigenicity of human rhabdomyosarcomas.

et al. 1989

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“…We and others have reported previously that the mck enhancer is contained within the region between bp -1350 and -1048 5' of the mck transcription initiation site (14,24,27,52,53). As a first step toward identification of nuclear factors that interact with the mck enhancer region, we divided the 302-bp enhancer into two parts by digestion with AvaI and analyzed factor interactions within each part by using gel retardation assays.…”

Section: Resultsmentioning

confidence: 99%

A new myocyte-specific enhancer-binding factor that recognizes a conserved element associated with multiple muscle-specific genes.

Gossett¹,

Kelvin²,

Sternberg³

et al. 1989

Mol. Cell. Biol.

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582

422

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Exposure of skeletal myoblasts to growth factor-deficient medium results in transcriptional activation of muscle-specific genes, including the muscle creatine kinase gene (mck). Tissue specificity, developmental regulation, and high-level expression of mck are conferred primarily by a muscle-specific enhancer located between base pairs (bp) -1350 and -1048 relative to the transcription initiation site (E. A. Sternberg, G. Spizz, W. M. Perry, D. Vizard, T. Weil, and E. N. Olson, Mol. Cell. Biol. 8:2896-2909. To begin to define the regulatory mechanisms that mediate the selective activation of the mck enhancer in differentiating muscle cells, we have further delimited the boundaries of this enhancer and analyzed its interactions with nuclear factors from a variety of myogenic and nonmyogenic cell types. Deletion mutagenesis showed that the region between 1,204 and 1,095 bp upstream of mck functions as a weak muscle-specffic enhancer that is dependent on an adjacent enhancer element for strong activity. This adjacent activating element does not exhibit enhancer activity in single copy but acts as a strong enhancer when multimerized. Gel retardation assays combined with DNase I footprinting and diethyl pyrocarbonate interference showed that a nuclear factor from differentiated C2 myotubes and BC3H1 myocytes recognized a conserved A+T-rich sequence within the peripheral activating region. This myocyte-specific enhancer-binding factor, designated MEF-2, was undetectable in nuclear extracts from C2 or BC3H1 myoblasts or several nonmyogenic cell lines. MEF-2 was first detectable within 2 h after exposure of myoblasts to mitogen-deficient medium and increased in abundance for 24 to 48 h thereafter. The appearance of MEF-2 required ongoing protein synthesis and was prevented by fibroblast growth factor and type transforming growth factor, which block the induction of muscle-specific genes. A myoblast-specific factor that is down regulated within 4 h after removal of growth factors was also found to bind to the MEF-2 recognition site. A 10-bp sequence, which was shown by DNase I footprinting and diethyl pyrocarbonate interference to interact directly with MEF-2, was identified within the rat and human mck enhancers, the rat myosin light-chain (m1c)-113 enhancer, and the chicken cardiac mkc-2A promoter. Oligomers corresponding to the region of the mlc-113 enhancer, which encompasses this conserved sequence, bound MEF-2 and competed for its binding to the mck enhancer. These results thus provide evidence for a novel myocyte-specific enhancer-binding factor, MEF-2, that is expressed early in the differentiation program and is suppressed by specific polypeptide growth factors. The ability of MEF-2 to recognize conserved activating elements associated with multiple muscle-specific genes suggests that this factor may participate in the coordinate regulation of genes during myogenesis.Development requires precisely coordinated control of transcription. Differentiation of skeletal myoblasts to myotubes represents a well-defined sy...

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“…Reporter plasmids for muscle-specific transcription included the pMCK-CAT plasmid (Sternberg et al, 1988), the 4R-tkCAT reporter (Weintraub et al, 1990), and the myogenin reporter construct pMyo1565CAT (kindly provided by E.N. Olson, University of Texas Southwestern Medical Center, Dallas, TX).…”

Section: Transient Transfections and Chloramphenicol Acetyl Transferamentioning

confidence: 99%

Distinct Effects of Rac1 on Differentiation of Primary Avian Myoblasts

Gallo

Serafini

Castellani

et al. 1999

MBoC

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Rho family GTPases have been implicated in the regulation of the actin cytoskeleton in response to extracellular cues and in the transduction of signals from the membrane to the nucleus. Their role in development and cell differentiation, however, is little understood. Here we show that the transient expression of constitutively active Rac1 and Cdc42 in unestablished avian myoblasts is sufficient to cause inhibition of myogenin expression and block of the transition to the myocyte compartment, whereas activated RhoA affects myogenic differentiation only marginally. Activation of c-Jun N-terminal kinase (JNK) appears not to be essential for block of differentiation because, although Rac1 and Cdc42 GTPases modestly activate JNK in quail myoblasts, a Rac1 mutant defective for JNK activation can still inhibit myogenic differentiation. Stable expression of active Rac1, attained by infection with a recombinant retrovirus, is permissive for terminal differentiation, but the resulting myotubes accumulate severely reduced levels of muscle-specific proteins. This inhibition is the consequence of posttranscriptional events and suggests the presence of a novel level of regulation of myogenesis. We also show that myotubes expressing constitutively active Rac1 fail to assemble ordered sarcomeres. Conversely, a dominant-negative Rac1 variant accelerates sarcomere maturation and inhibits v-Src–induced selective disassembly of I-Z-I complexes. Collectively, our findings provide a role for Rac1 during skeletal muscle differentiation and strongly suggest that Rac1 is required downstream of v-Src in the signaling pathways responsible for the dismantling of tissue-specific supramolecular structures.

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A ras-dependent pathway abolishes activity of a muscle-specific enhancer upstream from the muscle creatine kinase gene.

Cited by 36 publications

References 68 publications

Expression of the MyoD1 muscle determination gene defines differentiation capability but not tumorigenicity of human rhabdomyosarcomas.

Expression of the MyoD1 muscle determination gene defines differentiation capability but not tumorigenicity of human rhabdomyosarcomas.

A new myocyte-specific enhancer-binding factor that recognizes a conserved element associated with multiple muscle-specific genes.

Distinct Effects of Rac1 on Differentiation of Primary Avian Myoblasts

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