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Angel R. Nebreda - One of the best experts on this subject based on the ideXlab platform.
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a two step inactivation mechanism of MYT1 ensures cdk1 cyclin b activation and meiosis i entry
Current Biology, 2010Co-Authors: Josue E Ruiz, Marçal Vilar, Angel R. NebredaAbstract:Summary Activation of CDK1 is essential for M-phase entry both in mitosis and meiosis. G2-arrested oocytes contain a pool of CDK1/cyclin B complexes that are maintained inactive because of the phosphorylation of CDK1 on Thr14 and Tyr15 by the Wee1 family protein kinase MYT1, whose inhibition suffices to induce meiosis I entry [1–5]. CDK1/XRINGO and p90Rsk can both phosphorylate and downregulate MYT1 activity in vitro [6, 7]. Here we identify five p90Rsk phosphorylation sites on MYT1 that are different from the CDK1/XRINGO sites, and we show how both kinases synergize during oocyte maturation to inhibit MYT1, ensuring meiotic progression. We found that phosphorylation of MYT1 by CDK1/XRINGO early during oocyte maturation not only downregulates MYT1 kinase activity but also facilitates the recruitment of p90Rsk and further phosphorylation of MYT1. Mutation of the five p90Rsk residues to alanine impairs MYT1 hyperphosphorylation during oocyte maturation and makes MYT1 resistant to the inhibition by p90Rsk. Importantly, MYT1 phosphorylated by p90Rsk does not interact with CDK1/cyclin B, ensuring that the inhibitory phosphorylations of CDK1 cannot take place after meiosis I entry and contributing to the all-or-none meiotic response.
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A two-step inactivation mechanism of MYT1 ensures CDK1/cyclin B activation and meiosis I entry.
Current Biology, 2010Co-Authors: E. Josué Ruiz, Marçal Vilar, Angel R. NebredaAbstract:Summary Activation of CDK1 is essential for M-phase entry both in mitosis and meiosis. G2-arrested oocytes contain a pool of CDK1/cyclin B complexes that are maintained inactive because of the phosphorylation of CDK1 on Thr14 and Tyr15 by the Wee1 family protein kinase MYT1, whose inhibition suffices to induce meiosis I entry [1–5]. CDK1/XRINGO and p90Rsk can both phosphorylate and downregulate MYT1 activity in vitro [6, 7]. Here we identify five p90Rsk phosphorylation sites on MYT1 that are different from the CDK1/XRINGO sites, and we show how both kinases synergize during oocyte maturation to inhibit MYT1, ensuring meiotic progression. We found that phosphorylation of MYT1 by CDK1/XRINGO early during oocyte maturation not only downregulates MYT1 kinase activity but also facilitates the recruitment of p90Rsk and further phosphorylation of MYT1. Mutation of the five p90Rsk residues to alanine impairs MYT1 hyperphosphorylation during oocyte maturation and makes MYT1 resistant to the inhibition by p90Rsk. Importantly, MYT1 phosphorylated by p90Rsk does not interact with CDK1/cyclin B, ensuring that the inhibitory phosphorylations of CDK1 cannot take place after meiosis I entry and contributing to the all-or-none meiotic response.
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meiotic inactivation of xenopus MYT1 by cdk xringo but not cdk cyclin via site specific phosphorylation
Molecular Cell, 2008Co-Authors: Josue E Ruiz, Tim Hunt, Angel R. NebredaAbstract:Cell-cycle progression is regulated by cyclin-dependent kinases (CDKs). CDK1 and CDK2 can be also activated by noncyclin proteins named RINGO/Speedy, which were identified as inducers of the G2/M transition in Xenopus oocytes. However, it is unclear how XRINGO triggers M phase entry in oocytes. We show here that XRINGO-activated CDKs can phosphorylate specific residues in the regulatory domain of MYT1, a Wee1 family kinase that plays a key role in the G2 arrest of oocytes. We have identified three Ser that are major phosphoacceptor sites for CDK/XRINGO but are poorly phosphorylated by CDK/cyclin. Phosphorylation of these Ser inhibits MYT1 activity, whereas their mutation makes MYT1 resistant to inhibition by CDK/XRINGO. Our results demonstrate that XRINGO-activated CDKs have different substrate specificity than the CDK/cyclin complexes. We also describe a mechanism of MYT1 regulation based on site-specific phosphorylation, which is likely to mediate the induction of G2/M transition in oocytes by XRINGO.
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Meiotic Inactivation of Xenopus MYT1 by CDK/XRINGO, but Not CDK/Cyclin, via Site-Specific Phosphorylation
Molecular Cell, 2008Co-Authors: E. Josué Ruiz, Tim Hunt, Angel R. NebredaAbstract:Cell-cycle progression is regulated by cyclin-dependent kinases (CDKs). CDK1 and CDK2 can be also activated by noncyclin proteins named RINGO/Speedy, which were identified as inducers of the G2/M transition in Xenopus oocytes. However, it is unclear how XRINGO triggers M phase entry in oocytes. We show here that XRINGO-activated CDKs can phosphorylate specific residues in the regulatory domain of MYT1, a Wee1 family kinase that plays a key role in the G2 arrest of oocytes. We have identified three Ser that are major phosphoacceptor sites for CDK/XRINGO but are poorly phosphorylated by CDK/cyclin. Phosphorylation of these Ser inhibits MYT1 activity, whereas their mutation makes MYT1 resistant to inhibition by CDK/XRINGO. Our results demonstrate that XRINGO-activated CDKs have different substrate specificity than the CDK/cyclin complexes. We also describe a mechanism of MYT1 regulation based on site-specific phosphorylation, which is likely to mediate the induction of G2/M transition in oocytes by XRINGO.
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A link between MAP kinase and p34cdc2/cyclin B during oocyte maturation: p90rsk phosphorylates and inactivates the p34cdc2 inhibitory kinase MYT1
The EMBO Journal, 1998Co-Authors: Amparo Palmer, Anne-claude Gavin, Angel R. NebredaAbstract:M-phase entry in eukaryotic cells is driven by activation of MPF, a regulatory factor composed of cyclin B and the protein kinase p34(cdc2). In G2-arrested Xenopus oocytes, there is a stock of p34(cdc2)/cyclin B complexes (pre-MPF) which is maintained in an inactive state by p34(cdc2) phosphorylation on Thr14 and Tyr15. This suggests an important role for the p34(cdc2) inhibitory kinase(s) such as Wee1 and MYT1 in regulating the G2-->M transition during oocyte maturation. MAP kinase (MAPK) activation is required for M-phase entry in Xenopus oocytes, but its precise contribution to the activation of pre-MPF is unknown. Here we show that the C-terminal regulatory domain of MYT1 specifically binds to p90(rsk), a protein kinase that can be phosphorylated and activated by MAPK. p90(rsk) in turn phosphorylates the C-terminus of MYT1 and down-regulates its inhibitory activity on p34(cdc2)/cyclin B in vitro. Consistent with these results, MYT1 becomes phosphorylated during oocyte maturation, and activation of the MAPK-p90(rsk) cascade can trigger some MYT1 phosphorylation prior to pre-MPF activation. We found that MYT1 preferentially associates with hyperphosphorylated p90(rsk), and complexes can be detected in immunoprecipitates from mature oocytes. Our results suggest that during oocyte maturation MAPK activates p90(rsk) and that p90(rsk) in turn down-regulates MYT1, leading to the activation of p34(cdc2)/cyclin B.
Lynn D. Hudson - One of the best experts on this subject based on the ideXlab platform.
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A tool for examining the role of the zinc finger myelin transcription factor 1 (MYT1) in neural development: MYT1 knock-in mice
Transgenic Research, 2011Co-Authors: Lynn D. Hudson, Elena Romm, Jo Ann Berndt, Joseph A. NielsenAbstract:The MYT1 family of transcription factors is unique among the many classes of zinc finger proteins in how the zinc-stabilized fingers contact the DNA helix. To examine the function of MYT1 in the developing nervous system, we generated mice in which MYT1 expression was replaced by an enhanced Green Fluorescent Protein fused to a Codon-improved Cre recombinase as a protein reporter. MYT1 knock-in mice die at birth, apparently due to improper innervation of their lungs. Elimination of MYT1 did not significantly affect the number or distribution of neural precursor cells that normally express MYT1 in the embryonic spinal cord. Nor was the general pattern of differentiated neurons altered in the embryonic spinal cord. The MYT1 knock-in mice should provide an important tool for identifying the in vivo targets of MYT1 action and unraveling the role of this structurally distinct zinc finger protein in neural development.
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Myelin transcription factor 1 function in oligodendrocyte development
Journal of Neurochemistry, 2008Co-Authors: Joseph A. Nielsen, Lynn D. Hudson, Regina C. ArmstrongAbstract:Myelin transcription factor 1 (MYT1) is a CCHC zinc-finger protein that is expressed in oligodendrocyte progenitors (OP) and is down-regulated as oligodendrocytes differentiate and accumulate proteolipid protein (PLP). MYT1 contains six zinc-finger DNA-binding domains, a putative acidic transcriptional activation domain, and an alpha-helical protein–protein interaction domain. MYT1 has two zinc-fingers near the N-terminus and four zinc-fingers (4F) near the C-terminus. Each set of zinc-fingers can bind to the PLP promoter. The objective of this study was to determine the function of MYT1 by expressing the 4F domain of MYT1, which lacks the putative transcriptional activation domain and protein–protein interaction domain. We predicted the 4F domain would compete for MYT1 response elements, and lacking other functional domains would interfere with endogenous MYT1 function. A retroviral expression system that included a FLAG epitope tag was used to ectopically express the 4F domain of MYT1 in cultured rat neonatal OPs. OPs and their progeny exhibited nuclear immunoreactivity for the 4F-FLAG fusion protein. Expression of 4F in OPs grown with PDGF and FGF mitogens reduced proliferation as compared to controls. In the absence of mitogens, expression of 4F inhibited the differentiation of OPs as assessed by morphological criteria, O1 immunostaining, and PLP mRNA expression. This 4F inhibition of OP differentiation along the oligodendrocyte pathway was not due to alternative differentiation along an astrocytic pathway. These data suggest that MYT1 regulates a critical transition in oligodendrocyte lineage development in modulating the OP proliferative response relative to terminal differentiation and myelin gene expression. Acknowledgements: Supported by USUHS grant RO70IE.
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MYT1 family recruits histone deacetylase to regulate neural transcription
Journal of Neurochemistry, 2005Co-Authors: Elena Romm, Joseph A. Nielsen, Jin G. Kim, Lynn D. HudsonAbstract:The myelin transcription factor 1 (MYT1) gene family is comprised of three zinc finger genes [MYT1, MYT1L (MYT1-Like) and NZF3] of the structurally unique CCHHC class that are expressed predominantly in the developing CNS. To understand the mechanism by which this family regulates neural differentiation, we searched for interaction partners. In both yeast and a mammalian two-hybrid system, MYT1 and MYT1L interacted with Sin3B, a protein that mediates transcriptional repression by binding to histone deacetylases (HDACs). MYT1–Sin3B complexes were co-immunoprecipitated from transfected mammalian cells and included HDAC1 and HDAC2. MYT1 and MYT1L could partner with all three Sin3B isoforms, the long form (Sin3BLF) that includes the HDAC-binding domain, and the two short forms (Sin3BSF293 and Sin3BSF302) that lack this domain and may consequently antagonize Sin3BLF/HDAC-mediated co-repression. MYT1 or MYT1L interactions with the HDAC-binding form of Sin3B conferred repression on a heterologous promoter. Oligodendrocytes were shown to express transcripts encoding each of the Sin3B isoforms. We present a model in which the MYT1 family of zinc finger proteins, when bound to a neural promoter, can recruit Sin3B. Depending on the relative availability of Sin3B isoforms, the MYT1 gene family may favor the silencing of genes during neural development.
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Myelin transcription factor 1 (MYT1) modulates the proliferation and differentiation of oligodendrocyte lineage cells.
Molecular and Cellular Neuroscience, 2004Co-Authors: Joseph A. Nielsen, Lynn D. Hudson, Jo Ann Berndt, Regina C. ArmstrongAbstract:Abstract Myelin transcription factor 1 (MYT1) is a zinc finger DNA-binding protein that is expressed in neural progenitors and oligodendrocyte lineage cells. This study examines the role of MYT1 in oligodendrocyte lineage cells by overexpressing putative functional domains, a four-zinc finger DNA-binding region (4FMYT1) or a central protein–protein interaction domain (CDMYT1), without the predicted transcriptional activation domain. In the presence of mitogens, overexpression of 4FMYT1 inhibited proliferation of oligodendrocyte progenitors, but not cell types (astrocytes and NIH3T3 cells) lacking endogenous MYT1. Expression of 4FMYT1 inhibited the differentiation of oligodendrocyte progenitors into oligodendrocytes as assessed by morphology, immunostaining, and myelin gene expression. Progenitor differentiation was similarly inhibited by expression of CDMYT1 but only partially suppressed by overexpression of the intact MYT1. These data indicate that MYT1 may regulate a critical transition point in oligodendrocyte lineage development by modulating oligodendrocyte progenitor proliferation relative to terminal differentiation and up-regulation of myelin gene transcription.
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Myelin transcription factor 1 (MYT1) of the oligodendrocyte lineage, along with a closely related CCHC zinc finger, is expressed in developing neurons in the mammalian central nervous system.
Journal of Neuroscience Research, 1997Co-Authors: Jin G. Kim, Regina C. Armstrong, Denes V. Agoston, Alexandra Robinsky, Claudia Wiese, James W. Nagle, Lynn D. HudsonAbstract:The establishment and operation of the nervous system requires genetic regulation by a network of DNA-binding proteins, among which is the zinc finger superfamily of transcription factors. We have cloned and characterized a member of the unusual Cys-Cys-His-Cys (also referred to as Cys2HisCys, CCHC, or C2HC) class of zinc finger proteins in the developing nervous system. The novel gene, MYT1-like (MYT1l), is highly homologous to the original representative of this class, Myelin transcription factor 1 (MYT1) (Kim and Hudson, 1992). The MYT1 gene maps to human chromosome 20, while MYT1L maps to a region of human chromosome 2. Both zinc finger proteins are found in neurons at early stages of differentiation, with germinal zone cells displaying intense staining for MYT1. Unlike MYT1, MYT1l has not been detected in the glial lineage. Neurons that express MYT1l also express TuJ1, which marks neurons around the period of terminal mitosis. The MYT1l protein resides in distinct domains within the neuronal nucleus, analogous to the discrete pattern previously noted for MYT1 (Armstrong et al.: 14:303–321, 1995). The developmental expression and localization of these two multifingered CCHC proteins suggests that each may play a role in the development of neurons and oligodendroglia in the mammalian central nervous system. J. Neurosci. Res. 50:272–290, 1997. © 1997 Wiley-Liss, Inc. This article is a US government work and, as such, is in the public domain in the United States of America.
Johannes Rudolph - One of the best experts on this subject based on the ideXlab platform.
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Autophosphorylation of Ser66 on Xenopus MYT1 is a Prerequisite for Meiotic Inactivation of MYT1
Cell Cycle, 2006Co-Authors: Kolbrun Kristjansdottir, Alexias Safi, Chirag Shah, Johannes RudolphAbstract:MYT1 is a dual-specificity kinase that contributes to the regulation of the cell cycle byadding inhibitory phosphates to the cyclin-dependent kinases (Cdk/cyclins). MYT1 is found to bephosphorylated and less active in M-phase compared to interphase. Although MYT1 can bephosphorylated by several different kinases in vitro, it is not well understood how MYT1 isregulated in vivo. Additionally, the interplay between phosphorylation by other kinases andautophosphorylation has not been investigated. Since phosphorylation is an important mode ofregulation for MYT1, we have investigated the properties and physiological significance of theautophosphorylation of MYT1 from Xenopus laevis (XMYT1). Using MALDI mass spectrometrywe have identified Ser66 and Ser76 as autophosphorylation sites. Autophosphorylation isimportant for the activity of XMYT1 in intact cells, as found by comparing the timing of the cellcycle in Xenopus oocytes expressing either exogenous wild type XMYT1 or itsautophosphorylation site mutants. Spe...
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Autophosphorylation of Ser66 on Xenopus MYT1 is a prerequisite for meiotic inactivation of MYT1.
Cell Cycle, 2006Co-Authors: Kolbrun Kristjansdottir, Alexias Safi, Chirag Shah, Johannes RudolphAbstract:MYT1 is a dual-specificity kinase that contributes to the regulation of the cell cycle by adding inhibitory phosphates to the cyclin-dependent kinases (Cdk/cyclins). MYT1 is found to be phosphorylated and less active in M-phase compared to interphase. Although MYT1 can be phosphorylated by several different kinases in vitro, it is not well understood how MYT1 is regulated in vivo. Additionally, the interplay between phosphorylation by other kinases and autophosphorylation has not been investigated. Since phosphorylation is an important mode of regulation for MYT1, we have investigated the properties and physiological significance of the autophosphorylation of MYT1 from Xenopus laevis (XMYT1). Using MALDI mass spectrometry we have identified Ser66 and Ser76 as autophosphorylation sites. Autophosphorylation is important for the activity of XMYT1 in intact cells, as found by comparing the timing of the cell cycle in Xenopus oocytes expressing either exogenous wild type XMYT1 or its autophosphorylation site mutants. Specifically, S66A is significantly more potent than wild type XMYT1 at delaying entry into meiosis and concomitantly is hypophosphorylated as evident by a loss of mobility shift. However, this cannot be accounted for by a simple increase in kinase activity towards Cdk/cyclins in vitro. We therefore propose that MYT1 catalyzed autophosphorylation of residue S66 is a prerequisite and/or trigger for the further phosphorylation and inactivation of MYT1. Thus autophosphorylation of MYT1 is a novel inhibitory mechanism that adds another layer of complexity to the phosphorylation-dependent mechanism of MYT1 regulation.
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A fluorescence polarization assay for native protein substrates of kinases.
Analytical Biochemistry, 2003Co-Authors: Kolbrun Kristjansdottir, Johannes RudolphAbstract:Abstract Protein phosphorylation is the mediator of many important cellular processes of signal transduction and cell regulation. Phosphorylation often occurs on multiple sites within a single protein, whereby the results of individual phosphorylations are not well defined. This is partially due to the lack of tools for analyzing specific phosphorylation states in a quantitative manner. We have developed a high-throughput, rapid, and quantitative method for the determination of the phosphorylation status of peptides and, more importantly, native protein substrates of kinases using a competitive fluorescence-based approach. We have applied our method to measuring the phosphorylation activity of the Wee1 and MYT1 kinases. Our technique allows one to monitor the bis-phosphorylation status of the Cdk2 protein using an antibody specific for bis-phosphorylated Cdk2 and a fluorescently labeled bis-phosphorylated Cdk2 peptide. We have used this assay to screen a library of 16 general kinase inhibitors against Wee1 and MYT1 activity. None of the inhibitors inhibited Wee1, but both staurosporine and K-252a inhibited MYT1, with IC 50 values of 9.2±3.6 and 4.0±1.3 μM , respectively.
Regina C. Armstrong - One of the best experts on this subject based on the ideXlab platform.
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Myelin transcription factor 1 function in oligodendrocyte development
Journal of Neurochemistry, 2008Co-Authors: Joseph A. Nielsen, Lynn D. Hudson, Regina C. ArmstrongAbstract:Myelin transcription factor 1 (MYT1) is a CCHC zinc-finger protein that is expressed in oligodendrocyte progenitors (OP) and is down-regulated as oligodendrocytes differentiate and accumulate proteolipid protein (PLP). MYT1 contains six zinc-finger DNA-binding domains, a putative acidic transcriptional activation domain, and an alpha-helical protein–protein interaction domain. MYT1 has two zinc-fingers near the N-terminus and four zinc-fingers (4F) near the C-terminus. Each set of zinc-fingers can bind to the PLP promoter. The objective of this study was to determine the function of MYT1 by expressing the 4F domain of MYT1, which lacks the putative transcriptional activation domain and protein–protein interaction domain. We predicted the 4F domain would compete for MYT1 response elements, and lacking other functional domains would interfere with endogenous MYT1 function. A retroviral expression system that included a FLAG epitope tag was used to ectopically express the 4F domain of MYT1 in cultured rat neonatal OPs. OPs and their progeny exhibited nuclear immunoreactivity for the 4F-FLAG fusion protein. Expression of 4F in OPs grown with PDGF and FGF mitogens reduced proliferation as compared to controls. In the absence of mitogens, expression of 4F inhibited the differentiation of OPs as assessed by morphological criteria, O1 immunostaining, and PLP mRNA expression. This 4F inhibition of OP differentiation along the oligodendrocyte pathway was not due to alternative differentiation along an astrocytic pathway. These data suggest that MYT1 regulates a critical transition in oligodendrocyte lineage development in modulating the OP proliferative response relative to terminal differentiation and myelin gene expression. Acknowledgements: Supported by USUHS grant RO70IE.
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Myelin transcription factor 1 (MYT1) expression in demyelinated lesions of rodent and human CNS.
Glia, 2007Co-Authors: Adam C. Vana, Claudia F. Lucchinetti, Regina C. ArmstrongAbstract:Myelin transcription factor 1 (MYT1) is a zinc-finger DNA binding protein that influences developing oligodendrocyte progenitor (OP) cell proliferation, differentiation, and myelin gene transcription in vitro. The potential of MYT1 to play a role in OP responses leading to remyelination was examined using murine hepatitis virus strain A59 (MHV) to induce spinal cord demyelination and potential relevance to human pathology was evaluated in multiple sclerosis (MS) lesions. In MHV-infected mice, the density of MYT1 expressing cells markedly increased in lesioned areas of spinal cord white matter. MYT1 expressing cells proliferated most extensively during active demyelination and subsequently accumulated to maximal levels during early remyelination. Cells with nuclear MYT1 immunoreactivity were mainly OP cells, identified by co-localization with platelet-derived growth factor alpha receptor, with additional phenotypes being either oligodendrocytes or neural stem cells, identified by CC1 antigen and Musashi1, respectively. The density of OP cells expressing MYT1 was significantly increased in white matter of MHV-infected mice during demyelination and early remyelination then as remyelination advanced the values returned to levels comparable to PBS-injected control mice. In MHV lesions, MYT1 was not expressed in astrocytes, lymphocytes, or macrophage/microglial cells. MS lesions demonstrated increased MYT1 expression in both the periplaque white matter adjacent to lesions and within early remyelinating lesions. These results suggesta potential role for MYT1 in the regeneration of oligodendrocyte lineage cells in response to demyelination. © 2007 Wiley-Liss, Inc.
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Myelin transcription factor 1 (MYT1) modulates the proliferation and differentiation of oligodendrocyte lineage cells.
Molecular and Cellular Neuroscience, 2004Co-Authors: Joseph A. Nielsen, Lynn D. Hudson, Jo Ann Berndt, Regina C. ArmstrongAbstract:Abstract Myelin transcription factor 1 (MYT1) is a zinc finger DNA-binding protein that is expressed in neural progenitors and oligodendrocyte lineage cells. This study examines the role of MYT1 in oligodendrocyte lineage cells by overexpressing putative functional domains, a four-zinc finger DNA-binding region (4FMYT1) or a central protein–protein interaction domain (CDMYT1), without the predicted transcriptional activation domain. In the presence of mitogens, overexpression of 4FMYT1 inhibited proliferation of oligodendrocyte progenitors, but not cell types (astrocytes and NIH3T3 cells) lacking endogenous MYT1. Expression of 4FMYT1 inhibited the differentiation of oligodendrocyte progenitors into oligodendrocytes as assessed by morphology, immunostaining, and myelin gene expression. Progenitor differentiation was similarly inhibited by expression of CDMYT1 but only partially suppressed by overexpression of the intact MYT1. These data indicate that MYT1 may regulate a critical transition point in oligodendrocyte lineage development by modulating oligodendrocyte progenitor proliferation relative to terminal differentiation and up-regulation of myelin gene transcription.
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Myelin transcription factor 1 (MYT1) of the oligodendrocyte lineage, along with a closely related CCHC zinc finger, is expressed in developing neurons in the mammalian central nervous system.
Journal of Neuroscience Research, 1997Co-Authors: Jin G. Kim, Regina C. Armstrong, Denes V. Agoston, Alexandra Robinsky, Claudia Wiese, James W. Nagle, Lynn D. HudsonAbstract:The establishment and operation of the nervous system requires genetic regulation by a network of DNA-binding proteins, among which is the zinc finger superfamily of transcription factors. We have cloned and characterized a member of the unusual Cys-Cys-His-Cys (also referred to as Cys2HisCys, CCHC, or C2HC) class of zinc finger proteins in the developing nervous system. The novel gene, MYT1-like (MYT1l), is highly homologous to the original representative of this class, Myelin transcription factor 1 (MYT1) (Kim and Hudson, 1992). The MYT1 gene maps to human chromosome 20, while MYT1L maps to a region of human chromosome 2. Both zinc finger proteins are found in neurons at early stages of differentiation, with germinal zone cells displaying intense staining for MYT1. Unlike MYT1, MYT1l has not been detected in the glial lineage. Neurons that express MYT1l also express TuJ1, which marks neurons around the period of terminal mitosis. The MYT1l protein resides in distinct domains within the neuronal nucleus, analogous to the discrete pattern previously noted for MYT1 (Armstrong et al.: 14:303–321, 1995). The developmental expression and localization of these two multifingered CCHC proteins suggests that each may play a role in the development of neurons and oligodendroglia in the mammalian central nervous system. J. Neurosci. Res. 50:272–290, 1997. © 1997 Wiley-Liss, Inc. This article is a US government work and, as such, is in the public domain in the United States of America.
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High-grade human brain tumors exhibit increased expression of myelin transcription factor 1 (MYT1), a zinc finger DNA-binding protein.
Journal of Neuropathology and Experimental Neurology, 1997Co-Authors: Regina C. Armstrong, Lynn D. Hudson, Jin G. Kim, Alain Migneault, Marya L. Shegog, Richard B. HesslerAbstract:Detection and characterization of distinct central nervous system (CNS) tumor cell types is clinically important since distinct tumor types are associated with different prognoses and treatments. However, there is currently a lack of markers to identify certain glioma types and insufficient understanding as to which cells give rise to different glioma cell types. In the present study, biopsy specimens from human brain tumors were analyzed for expression of Myelin Transcription Factor 1 (MYT1) to explore the extent to which glioma cells reflect characteristic expression of MYT1 in developing glial progenitor cells. Immunostaining with an antibody against MYT1 revealed widespread immunoreactivity that was most prominent in high-grade oligodendrogliomas, astrocytomas, and mixed oligoastrocytomas as well as in a dysembryoplastic neuroepithelial tumor. MYT1 immunoreactivity in tumor regions generally correlated with the prevalence of cells exhibiting nuclear immunolabeling with an antibody against Ki-67, suggesting an association of MYT1 with cell proliferation that was also observed in normal adult human and rat brain in the germinal subependymal zone. The MYT1 immunoreactivity was frequently nuclear, appearing as dotted or punctate, but in some cases it was localized to the cytoplasm. In combination with histopathological studies and analysis of Ki-67 immunoreactivity, examination of MYT1 immunolabeling may provide additional information to aid in the detection and diagnosis of CNS tumors.
Joseph A. Nielsen - One of the best experts on this subject based on the ideXlab platform.
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A tool for examining the role of the zinc finger myelin transcription factor 1 (MYT1) in neural development: MYT1 knock-in mice
Transgenic Research, 2011Co-Authors: Lynn D. Hudson, Elena Romm, Jo Ann Berndt, Joseph A. NielsenAbstract:The MYT1 family of transcription factors is unique among the many classes of zinc finger proteins in how the zinc-stabilized fingers contact the DNA helix. To examine the function of MYT1 in the developing nervous system, we generated mice in which MYT1 expression was replaced by an enhanced Green Fluorescent Protein fused to a Codon-improved Cre recombinase as a protein reporter. MYT1 knock-in mice die at birth, apparently due to improper innervation of their lungs. Elimination of MYT1 did not significantly affect the number or distribution of neural precursor cells that normally express MYT1 in the embryonic spinal cord. Nor was the general pattern of differentiated neurons altered in the embryonic spinal cord. The MYT1 knock-in mice should provide an important tool for identifying the in vivo targets of MYT1 action and unraveling the role of this structurally distinct zinc finger protein in neural development.
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Myelin transcription factor 1 function in oligodendrocyte development
Journal of Neurochemistry, 2008Co-Authors: Joseph A. Nielsen, Lynn D. Hudson, Regina C. ArmstrongAbstract:Myelin transcription factor 1 (MYT1) is a CCHC zinc-finger protein that is expressed in oligodendrocyte progenitors (OP) and is down-regulated as oligodendrocytes differentiate and accumulate proteolipid protein (PLP). MYT1 contains six zinc-finger DNA-binding domains, a putative acidic transcriptional activation domain, and an alpha-helical protein–protein interaction domain. MYT1 has two zinc-fingers near the N-terminus and four zinc-fingers (4F) near the C-terminus. Each set of zinc-fingers can bind to the PLP promoter. The objective of this study was to determine the function of MYT1 by expressing the 4F domain of MYT1, which lacks the putative transcriptional activation domain and protein–protein interaction domain. We predicted the 4F domain would compete for MYT1 response elements, and lacking other functional domains would interfere with endogenous MYT1 function. A retroviral expression system that included a FLAG epitope tag was used to ectopically express the 4F domain of MYT1 in cultured rat neonatal OPs. OPs and their progeny exhibited nuclear immunoreactivity for the 4F-FLAG fusion protein. Expression of 4F in OPs grown with PDGF and FGF mitogens reduced proliferation as compared to controls. In the absence of mitogens, expression of 4F inhibited the differentiation of OPs as assessed by morphological criteria, O1 immunostaining, and PLP mRNA expression. This 4F inhibition of OP differentiation along the oligodendrocyte pathway was not due to alternative differentiation along an astrocytic pathway. These data suggest that MYT1 regulates a critical transition in oligodendrocyte lineage development in modulating the OP proliferative response relative to terminal differentiation and myelin gene expression. Acknowledgements: Supported by USUHS grant RO70IE.
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MYT1 family recruits histone deacetylase to regulate neural transcription
Journal of Neurochemistry, 2005Co-Authors: Elena Romm, Joseph A. Nielsen, Jin G. Kim, Lynn D. HudsonAbstract:The myelin transcription factor 1 (MYT1) gene family is comprised of three zinc finger genes [MYT1, MYT1L (MYT1-Like) and NZF3] of the structurally unique CCHHC class that are expressed predominantly in the developing CNS. To understand the mechanism by which this family regulates neural differentiation, we searched for interaction partners. In both yeast and a mammalian two-hybrid system, MYT1 and MYT1L interacted with Sin3B, a protein that mediates transcriptional repression by binding to histone deacetylases (HDACs). MYT1–Sin3B complexes were co-immunoprecipitated from transfected mammalian cells and included HDAC1 and HDAC2. MYT1 and MYT1L could partner with all three Sin3B isoforms, the long form (Sin3BLF) that includes the HDAC-binding domain, and the two short forms (Sin3BSF293 and Sin3BSF302) that lack this domain and may consequently antagonize Sin3BLF/HDAC-mediated co-repression. MYT1 or MYT1L interactions with the HDAC-binding form of Sin3B conferred repression on a heterologous promoter. Oligodendrocytes were shown to express transcripts encoding each of the Sin3B isoforms. We present a model in which the MYT1 family of zinc finger proteins, when bound to a neural promoter, can recruit Sin3B. Depending on the relative availability of Sin3B isoforms, the MYT1 gene family may favor the silencing of genes during neural development.
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Myelin transcription factor 1 (MYT1) modulates the proliferation and differentiation of oligodendrocyte lineage cells.
Molecular and Cellular Neuroscience, 2004Co-Authors: Joseph A. Nielsen, Lynn D. Hudson, Jo Ann Berndt, Regina C. ArmstrongAbstract:Abstract Myelin transcription factor 1 (MYT1) is a zinc finger DNA-binding protein that is expressed in neural progenitors and oligodendrocyte lineage cells. This study examines the role of MYT1 in oligodendrocyte lineage cells by overexpressing putative functional domains, a four-zinc finger DNA-binding region (4FMYT1) or a central protein–protein interaction domain (CDMYT1), without the predicted transcriptional activation domain. In the presence of mitogens, overexpression of 4FMYT1 inhibited proliferation of oligodendrocyte progenitors, but not cell types (astrocytes and NIH3T3 cells) lacking endogenous MYT1. Expression of 4FMYT1 inhibited the differentiation of oligodendrocyte progenitors into oligodendrocytes as assessed by morphology, immunostaining, and myelin gene expression. Progenitor differentiation was similarly inhibited by expression of CDMYT1 but only partially suppressed by overexpression of the intact MYT1. These data indicate that MYT1 may regulate a critical transition point in oligodendrocyte lineage development by modulating oligodendrocyte progenitor proliferation relative to terminal differentiation and up-regulation of myelin gene transcription.
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Nuclear Organization and MYT1 Interaction in Transcriptional Control of Neural Cell Differentiation
2002Co-Authors: Joseph A. NielsenAbstract:Abstract : Neural cell differentiation is a complex set of events beginning with cells responding to both soluble and cell contact-dependent external signals. These signals activate pathways that lead to changes in gene expression patterns, which ultimately give rise to the differentiated cell phenotype. In these studies, potential mechanisms regulating different aspects of oligodendrocyte differentiation were explored. Specifically, these studies examined the contribution of gene and protein localization to the establishment and/or maintenance of terminally differentiated oligodendrocyte gene expression patterns and the role of myelin transcription factor 1 (MYT1) in the regulation of oligodendrocyte proliferation and differentiation. MYT1 is a zinc-finger DNA-binding protein that is expressed in neural progenitors and is localized to discrete domains within the nucleus of oligodendrocyte progenitors. Primary oligodendrocyte lineage cells were examined during cell differentiation in order to study the localization of the highly expressed tissue-specific proteolipid protein gene relative to nuclear proteins such as MYT1 and splicing factors within interphase nuclei. These data support a nuclear organization model in which nuclear proteins and genes exhibit specific patterns of distribution within nuclei, and activation of tissue-specific genes is associated with changes in protein distribution rather than changes in gene localization. MYT1 contains six zinc-finger DNA-binding domains with sets of two N-terminal and of four C-terminal zinc-fingers. A retroviral expression system was used to overexpress the four zinc-finger DNA-binding domain of MYT1 (4FMYT1) which lacks the putative domains for protein-protein interaction and transcriptional activation. In a dominant negative study, expression of 4FMYT1 inhibited both proliferation and differentiation of oligodendrocyte
