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Peter Lengyel - One of the best experts on this subject based on the ideXlab platform.
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the increase in levels of interferon inducible Proteins p202a and p202b and rna dependent Protein kinase pkr during myoblast differentiation is due to transactivation by MyoD their tissue distribution in uninfected mice does not depend on interferons
Journal of Interferon and Cytokine Research, 2002Co-Authors: H Wang, B Ding, Chuanju Liu, X Y, Stephane Deschamps, Bruce A Roe, Peter LengyelAbstract:The murine 200 family Proteins p202a, p202b, and p204, and also RNA-dependent Protein kinase (PKR) are inducible by interferons (IFNs). p202a, p202b, and p204 modulate the activity of a large variety of transcription factors and also are involved in muscle differentiation. PKR is a multifunctional serine/threonine kinase, which is involved in antiviral defense and cell growth control and in the response to various stress signals. We reported earlier that the level of p204 increases during cultured C2C12 myoblast differentiation to myotubes in consequence of transactivation by the skeletal muscle-specific MyoD Protein. The levels of p202a, p202b, and PKR also increase during the differentiation. We report here that these increased Protein levels also are due to the transactivation of their genes by MyoD. This is made possible by the occurrence in each of these genes of at least six E boxes, which are recognition sites for MyoD. We also show that the distribution of the p204, p202a, p202b, and PKR Proteins ...
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the MyoD inducible p204 Protein overcomes the inhibition of myoblast differentiation by id Proteins
Molecular and Cellular Biology, 2002Co-Authors: Chuanju Liu, Bo Ding, Hong Wang, Peter LengyelAbstract:The murine p204 Protein level is highest in heart and skeletal muscle. During the fusion of cultured myoblasts to myotubes, the p204 level increases due to transcription dependent on the muscle-specific MyoD Protein, and p204 is phosphorylated and translocated from the nucleus to the cytoplasm. p204 overexpression accelerates myoblast fusion in differentiation medium and triggers this process even in growth medium. Here we report that p204 is required for the differentiation of C2C12 myoblasts. We propose that it enables the differentiation, at least in part, by overcoming the inhibition of the activities of the MyoD and E47 Proteins by the Id Proteins: Id1, Id2, and Id3. These are known to inhibit skeletal muscle differentiation by binding and blocking the activity of MyoD, E12/E47, and other myogenic basic helix-loop-helix (bHLH) Proteins. Our hypothesis is based on the following findings. (i) A decrease in the p204 level in C2C12 myoblasts by antisense RNA (a) increased the level of the Id2; (b) inhibited the MyoD-, E12/E47-, and other bHLH Protein-dependent accumulation of the muscle-specific myosin heavy-chain Protein; and (c) inhibited the fusion of myoblasts to myotubes in differentiation medium. (ii) p204 bound to the Id Proteins in vitro and in vivo. (iii) In the binding of p204 to Id2, the b segment of p204 and the HLH segment of Id2 were involved. (iv) Addition of p204 overcame the inhibition by the Id Proteins of the binding of MyoD and E47 to DNA in vitro. (v) Overexpression of p204 in myoblasts (a) decreased the level of the Id Proteins, even in a culture in growth medium, and (b) overcame the inhibition by the Id Proteins of MyoD- and E47 dependent transcription and also overcame the inhibition by Id2 of the fusion of myoblasts to myotubes.
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increase in p202 expression during skeletal muscle differentiation inhibition of MyoD Protein expression and activity by p202
Molecular and Cellular Biology, 1998Co-Authors: Bansidhar Datta, Wang Min, Sandeep Burma, Peter LengyelAbstract:p202 is a primarily nuclear, interferon-inducible murine Protein that is encoded by the Ifi 202 gene. Overexpression of p202 in transfected cells retards cell proliferation. p202 modulates the pattern of gene expression by inhibiting the activity of various transcription factors including NF-kappaB, c-Fos, c-Jun, E2F-1, and p53. Here we report that p202 was constitutively expressed in mouse skeletal muscle and that the levels of 202 RNA and p202 greatly increased during the differentiation of cultured C2C12 myoblasts to myotubes. When overexpressed in transfected myoblasts, p202 inhibited the expression of one muscle Protein (MyoD) without affecting the expression of a second one (myogenin). Thus, the decrease in the level of MyoD (but not of myogenin) during muscle differentiation may be the consequence of the increase in p202 level. Overexpressed p202 also inhibited the transcriptional activity of both MyoD and myogenin. This inhibition was correlated with an interaction of p202 with both Proteins, as well as the inhibition by p202 of the sequence-specific binding of both Proteins to DNA. This inhibition of the expression of MyoD and of the transcriptional activity of MyoD and myogenin may account for the inhibition of the induction of myoblast differentiation by premature overexpression of p202.
Anne Fernandez - One of the best experts on this subject based on the ideXlab platform.
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crosstalk between cell cycle regulators and the myogenic factor MyoD in skeletal myoblasts
Cellular and Molecular Life Sciences, 2001Co-Authors: Magali Kitzmann, Anne FernandezAbstract:During the early process of skeletal muscle differentiation, myogenic factors are not only involved in muscle-specific gene induction but also in regulating the transition from the proliferative stage, when MyoD and Myf5 are already expressed, to the orderly exit from the cell division cycle. This key step in skeletal muscle differentiation involves the down-regulation of cell cycle activators such as cyclins and cdks, and up-regulation of cell cycle inhibitors such as Rb, p21, p27, and p57. In particular, Rb and p21 have been shown to play an important role in the growth arrest of differentiating myoblasts. Their level and/or activity, while being negatively controlled by growth factors, appear to be positively linked with the myogenic factor MyoD, which plays a cooperative role in the induction of growth arrest. MyoD can block proliferation independently of its transcriptional activity. Therefore, the interplay between G1 cyclins and cdk inhibitors, on the one hand, and MyoD and its cofactors, on the other, plays a critical role in myoblast cell cycle withdrawal. Accurate synchronization of dividing myoblasts revealed that MyoD and Myf5 are themselves subject to specific cell cycle-dependent regulation, with MyoD at its highest level in early G1 and its lowest level at the G1 to S phase transition. The time-window when cells exit their cycle into differentiation is in G1, when MyoD is maximal and Myf5 is down. In contrast, quiescent non-differentiating myoblasts (i.e., in G0) present an opposite pattern for the two factors: high Myf5 and no MyoD. Several recent studies have focused on MyoD phosphorylation and its potential role in ubiquitination-mediated degradation of the Protein. Linking this phosphorylation to the cell cycle-dependent drop in MyoD Protein before S phase leads, to a mechanism implying cdk2-cyclin E and its inhibitors (p57kip and p21cip) in the tight control of MyoD levels and subsequent myoblast cell cycle progression or exit into differentiation.
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rhoa gtpase and serum response factor control selectively the expression of MyoD without affecting myf5 in mouse myoblasts
Molecular Biology of the Cell, 1998Co-Authors: Gilles Carnac, Magali Kitzmann, Michael Primig, Philippe Chafey, David Tuil, Ned J C Lamb, Anne FernandezAbstract:MyoD and Myf5 belong to the family of basic helix-loop-helix transcription factors that are key operators in skeletal muscle differentiation. MyoD and Myf5 genes are selectively activated during development in a time and region-specific manner and in response to different stimuli. However, molecules that specifically regulate the expression of these two genes and the pathways involved remain to be determined. We have recently shown that the serum response factor (SRF), a transcription factor involved in activation of both mitogenic response and muscle differentiation, is required for MyoD gene expression. We have investigated here whether SRF is also involved in the control of Myf5 gene expression, and the potential role of upstream regulators of SRF activity, the Rho family G-Proteins including Rho, Rac, and CDC42, in the regulation of MyoD and Myf5. We show that inactivation of SRF does not alter Myf5 gene expression, whereas it causes a rapid extinction of MyoD gene expression. Furthermore, we show that RhoA, but not Rac or CDC42, is also required for the expression of MyoD. Indeed, blocking the activity of G-Proteins using the general inhibitor lovastatin, or more specific antagonists of Rho Proteins such as C3-transferase or dominant negative RhoA Protein, resulted in a dramatic decrease of MyoD Protein levels and promoter activity without any effects on Myf5 expression. We further show that RhoA-dependent transcriptional activation required functional SRF in C2 muscle cells. These data illustrate that MyoD and Myf5 are regulated by different upstream activation pathways in which MyoD expression is specifically modulated by a RhoA/SRF signaling cascade. In addition, our results establish the first link between RhoA Protein activity and the expression of a key muscle regulator.
Magali Kitzmann - One of the best experts on this subject based on the ideXlab platform.
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crosstalk between cell cycle regulators and the myogenic factor MyoD in skeletal myoblasts
Cellular and Molecular Life Sciences, 2001Co-Authors: Magali Kitzmann, Anne FernandezAbstract:During the early process of skeletal muscle differentiation, myogenic factors are not only involved in muscle-specific gene induction but also in regulating the transition from the proliferative stage, when MyoD and Myf5 are already expressed, to the orderly exit from the cell division cycle. This key step in skeletal muscle differentiation involves the down-regulation of cell cycle activators such as cyclins and cdks, and up-regulation of cell cycle inhibitors such as Rb, p21, p27, and p57. In particular, Rb and p21 have been shown to play an important role in the growth arrest of differentiating myoblasts. Their level and/or activity, while being negatively controlled by growth factors, appear to be positively linked with the myogenic factor MyoD, which plays a cooperative role in the induction of growth arrest. MyoD can block proliferation independently of its transcriptional activity. Therefore, the interplay between G1 cyclins and cdk inhibitors, on the one hand, and MyoD and its cofactors, on the other, plays a critical role in myoblast cell cycle withdrawal. Accurate synchronization of dividing myoblasts revealed that MyoD and Myf5 are themselves subject to specific cell cycle-dependent regulation, with MyoD at its highest level in early G1 and its lowest level at the G1 to S phase transition. The time-window when cells exit their cycle into differentiation is in G1, when MyoD is maximal and Myf5 is down. In contrast, quiescent non-differentiating myoblasts (i.e., in G0) present an opposite pattern for the two factors: high Myf5 and no MyoD. Several recent studies have focused on MyoD phosphorylation and its potential role in ubiquitination-mediated degradation of the Protein. Linking this phosphorylation to the cell cycle-dependent drop in MyoD Protein before S phase leads, to a mechanism implying cdk2-cyclin E and its inhibitors (p57kip and p21cip) in the tight control of MyoD levels and subsequent myoblast cell cycle progression or exit into differentiation.
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rhoa gtpase and serum response factor control selectively the expression of MyoD without affecting myf5 in mouse myoblasts
Molecular Biology of the Cell, 1998Co-Authors: Gilles Carnac, Magali Kitzmann, Michael Primig, Philippe Chafey, David Tuil, Ned J C Lamb, Anne FernandezAbstract:MyoD and Myf5 belong to the family of basic helix-loop-helix transcription factors that are key operators in skeletal muscle differentiation. MyoD and Myf5 genes are selectively activated during development in a time and region-specific manner and in response to different stimuli. However, molecules that specifically regulate the expression of these two genes and the pathways involved remain to be determined. We have recently shown that the serum response factor (SRF), a transcription factor involved in activation of both mitogenic response and muscle differentiation, is required for MyoD gene expression. We have investigated here whether SRF is also involved in the control of Myf5 gene expression, and the potential role of upstream regulators of SRF activity, the Rho family G-Proteins including Rho, Rac, and CDC42, in the regulation of MyoD and Myf5. We show that inactivation of SRF does not alter Myf5 gene expression, whereas it causes a rapid extinction of MyoD gene expression. Furthermore, we show that RhoA, but not Rac or CDC42, is also required for the expression of MyoD. Indeed, blocking the activity of G-Proteins using the general inhibitor lovastatin, or more specific antagonists of Rho Proteins such as C3-transferase or dominant negative RhoA Protein, resulted in a dramatic decrease of MyoD Protein levels and promoter activity without any effects on Myf5 expression. We further show that RhoA-dependent transcriptional activation required functional SRF in C2 muscle cells. These data illustrate that MyoD and Myf5 are regulated by different upstream activation pathways in which MyoD expression is specifically modulated by a RhoA/SRF signaling cascade. In addition, our results establish the first link between RhoA Protein activity and the expression of a key muscle regulator.
A Fernandez - One of the best experts on this subject based on the ideXlab platform.
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Nuclear import of the myogenic factor MyoD requires cAMP-dependent Protein kinase activity but not the direct phosphorylation of MyoD.
Journal of cell science, 1994Co-Authors: M Vandromme, G Carnac, C Gauthier-rouvière, D Fesquet, N Lamb, A FernandezAbstract:MyoD is a nuclear phosphoProtein that belongs to the family of myogenic regulatory factors and acts in the transcriptional activation of muscle-specific genes. We have investigated the role of cAMP-dependent Protein kinase (A-kinase) in modulating the nuclear locale of MyoD. Purified MyoD Protein microinjected into the cytoplasm of rat embryo fibroblasts is rapidly translocated into the nucleus. Inhibition of A-kinase activity through injection of the specific inhibitory peptide PKI prevents this nuclear localisation. This inhibition of nuclear location is specifically reversed by injection of purified A-kinase catalytic subunit, showing the requirement for A-kinase in the nuclear import of MyoD. Site-directed mutagenesis of all the putative sites for A-kinase-dependent phosphorylation on MyoD, substituting serine or threonine residues for the non-phosphorylatable amino acid alanine, had no effect on nuclear import of mutated MyoD. These data exclude the possibility that the effect of A-kinase on the nuclear translocation of MyoD is mediated by direct phosphorylation of MyoD and imply that A-kinase operates through phosphorylation of components involved in the nuclear transport of MyoD.
Ashok Kumar - One of the best experts on this subject based on the ideXlab platform.
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tumor necrosis factor like weak inducer of apoptosis inhibits skeletal myogenesis through sustained activation of nuclear factor κb and degradation of MyoD Protein
Journal of Biological Chemistry, 2006Co-Authors: Charu Dogra, Harish Changotra, Subburaman Mohan, Ashok KumarAbstract:In this study we have investigated the effect and the mechanisms by which tumor necrosis factor-like weak inducer of apoptosis (TWEAK) modulates myogenic differentiation. Treatment of C2C12 myoblasts with TWEAK inhibited their differentiation evident by a decrease in the expression of creatine kinase, myosin heavy chain-fast twitch, myogenin, and the formation of multinucleated myotubes. TWEAK also inhibited the differentiation of mouse primary myoblasts. Conversely, the proliferation of C2C12 myoblasts and the expression of a cell-cycle regulator cyclin D1 were increased in response to TWEAK treatment. Inhibition of cellular proliferation using hydroxyurea only partially reversed the inhibitory effect of TWEAK on myogenic differentiation. Treatment of C2C12 myoblasts with TWEAK resulted in the activation of nuclear factor-kappaB (NF-kappaB), the (IkappaB) IkappaB kinase (IKK) complex, and the phosphorylation and degradation of IkappaBalpha Protein. Inhibition of NF-kappaB activity by overexpression of a dominant negative mutant of IkappaBalpha (IkappaBalphaDeltaN) significantly increased the myogenic differentiation in TWEAK-treated C2C12 cultures. Furthermore, overexpression of a dominant negative mutant of IKKbeta (IKKbetaK44A) but not IKKalpha (IKKalphaK44M) reversed the inhibitory effect of TWEAK on myogenesis. TWEAK inhibited the expression of myogenic regulatory factors MyoD and myogenin and also induced the degradation of MyoD Protein. Finally, inhibition of NF-kappaB activation through overexpression of IKKbetaK44A prevented the degradation of MyoD Protein. Overall, our data suggest that TWEAK inhibits myogenesis through the activation of NF-kappaB signaling pathway and degradation of MyoD Protein.
