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Breen TR. Mutant alleles of the Drosophila trithorax gene produce common and unusual homeotic and other developmental phenotypes. Genetics 1999; 152:319-44. [PMID: 10224264 PMCID: PMC1460610 DOI: 10.1093/genetics/152.1.319] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
trithorax (trx) encodes chromosome-binding proteins required throughout embryogenesis and imaginal development for tissue- and cell-specific levels of transcription of many genes including homeotic genes of the ANT-C and BX-C. trx encodes two protein isoforms that contain conserved motifs including a C-terminal SET domain, central PHD fingers, an N-terminal DNA-binding homology, and two short motifs also found in the TRX human homologue, ALL1. As a first step to characterizing specific developmental functions of TRX, I examined phenotypes of 420 combinations of 21 trx alleles. Among these are 8 hypomorphic alleles that are sufficient for embryogenesis but provide different levels of trx function at homeotic genes in imaginal cells. One allele alters the N terminus of TRX, which severely impairs larval and imaginal growth. Hypomorphic alleles that alter different regions of TRX equivalently reduce function at affected genes, suggesting TRX interacts with common factors at different target genes. All hypomorphic alleles examined complement one another, suggesting cooperative TRX function at target genes. Comparative effects of hypomorphic genotypes support previous findings that TRX has tissue-specific interactions with other factors at each target gene. Some hypomorphic genotypes also produce phenotypes that suggest TRX may be a component of signal transduction pathways that provide tissue- and cell-specific levels of target gene transcription.
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Affiliation(s)
- T R Breen
- Department of Zoology, Southern Illinois University, Carbondale, Illinois 62901-6501, USA.
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152
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Aagaard L, Laible G, Selenko P, Schmid M, Dorn R, Schotta G, Kuhfittig S, Wolf A, Lebersorger A, Singh PB, Reuter G, Jenuwein T. Functional mammalian homologues of the Drosophila PEV-modifier Su(var)3-9 encode centromere-associated proteins which complex with the heterochromatin component M31. EMBO J 1999; 18:1923-38. [PMID: 10202156 PMCID: PMC1171278 DOI: 10.1093/emboj/18.7.1923] [Citation(s) in RCA: 343] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The chromo and SET domains are conserved sequence motifs present in chromosomal proteins that function in epigenetic control of gene expression, presumably by modulating higher order chromatin. Based on sequence information from the SET domain, we have isolated human (SUV39H1) and mouse (Suv39h1) homologues of the dominant Drosophila modifier of position-effect-variegation (PEV) Su(var)3-9. Mammalian homologues contain, in addition to the SET domain, the characteristic chromo domain, a combination that is also preserved in the Schizosaccharyomyces pombe silencing factor clr4. Chromatin-dependent gene regulation is demonstrated by the potential of human SUV39H1 to increase repression of the pericentromeric white marker gene in transgenic flies. Immunodetection of endogenous Suv39h1/SUV39H1 proteins in a variety of mammalian cell lines reveals enriched distribution at heterochromatic foci during interphase and centromere-specific localization during metaphase. In addition, Suv39h1/SUV39H1 proteins associate with M31, currently the only other characterized mammalian SU(VAR) homologue. These data indicate the existence of a mammalian SU(VAR) complex and define Suv39h1/SUV39H1 as novel components of mammalian higher order chromatin.
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Affiliation(s)
- L Aagaard
- Research Institute of Molecular Pathology (IMP), The Vienna Biocenter, Dr. Bohrgasse 7, A-1030 Vienna, Austria
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153
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Callebaut I, Courvalin JC, Mornon JP. The BAH (bromo-adjacent homology) domain: a link between DNA methylation, replication and transcriptional regulation. FEBS Lett 1999; 446:189-93. [PMID: 10100640 DOI: 10.1016/s0014-5793(99)00132-5] [Citation(s) in RCA: 152] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Using sensitive methods of sequence analysis including hydrophobic cluster analysis, we report here a hitherto undescribed family of modules, the BAH (bromo-adjacent homology) family, which includes proteins such as eukaryotic DNA (cytosine-5) methyltransferases, the origin recognition complex 1 (Orc1) proteins, as well as several proteins involved in transcriptional regulation. The BAH domain appears to act as a protein-protein interaction module specialized in gene silencing, as suggested for example by its interaction within yeast Orc1p with the silent information regulator Sir1p. The BAH module might therefore play an important role by linking DNA methylation, replication and transcriptional regulation.
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Affiliation(s)
- I Callebaut
- Systèmes moléculaires and Biologie structurale, LMCP, CNRS UMR 7590, Université Paris 6, France.
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154
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Abstract
Many chromosome abnormalities, especially translocations of inversions, are closely associated with a particular morphologic or phenotypic subtype of leukemia, lymphoma, or sarcoma. Cloning the genes at the breakpoints of these rearrangements has had a major impact on our understanding of the molecular biology of cancer. One such gene is MLL (myeloid-lymphoid or mixed lineage leukemia) located at chromosome band 11q23. The target gene(s) of MLL is unknown at present, but because of its homology to the trithorax gene in Drosophila as well as experimental data from mice, it appears to be involved in maintaining the function of some of the homeobox genes. Most genes involved in translocations have homologs in other organisms. Comparison of the functions of these genes in human cells with their function in other systems has enriched our understanding of their role in cell biology.
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Affiliation(s)
- J D Rowley
- Section of Hematology/Oncology, University of Chicago Medical Center, Illinois 60637-1470, USA.
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155
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Corda Y, Schramke V, Longhese MP, Smokvina T, Paciotti V, Brevet V, Gilson E, Géli V. Interaction between Set1p and checkpoint protein Mec3p in DNA repair and telomere functions. Nat Genet 1999; 21:204-8. [PMID: 9988274 DOI: 10.1038/5991] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The yeast protein Set1p, inactivation of which alleviates telomeric position effect (TPE), contains a conserved SET domain present in chromosomal proteins involved in epigenetic control of transcription. Mec3p is required for efficient DNA-damage-dependent checkpoints at G1/S, intra-S and G2/M (refs 3-7). We show here that the SET domain of Set1p interacts with Mec3p. Deletion of SET1 increases the viability of mec3delta mutants after DNA damage (in a process that is mostly independent of Rad53p kinase, which has a central role in checkpoint control) but does not significantly affect cell-cycle progression. Deletion of MEC3 enhances TPE and attenuates the Set1delta-induced silencing defect. Furthermore, restoration of TPE in a Set1delta mutant by overexpression of the isolated SET domain requires Mec3p. Finally, deletion of MEC3 results in telomere elongation, whereas cells with deletions of both SET1 and MEC3 do not have elongated telomeres. Our findings indicate that interactions between SET1 and MEC3 have a role in DNA repair and telomere function.
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Affiliation(s)
- Y Corda
- Laboratoire d'Ingénierie et de Dynamique des Systèmes Macromoléculaires, CNRS, Marseille, France
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156
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Herman GE, Finegold M, Zhao W, de Gouyon B, Metzenberg A. Medical complications in long-term survivors with X-linked myotubular myopathy. J Pediatr 1999; 134:206-14. [PMID: 9931531 DOI: 10.1016/s0022-3476(99)70417-8] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
OBJECTIVES X-linked myotubular myopathy (MTM1) is a rare developmental disorder of skeletal muscle characterized by the presence of central nuclei in biopsy specimens from affected male subjects. Until recently, the disorder was usually fatal within the first year of life. This study was undertaken to determine the outcome in long-term survivors (>1 year of age) with MTM1. METHODS Clinical data were obtained on 55 male subjects from 49 independent North American families for which a mutation was identified in the X-linked myotubularin gene by direct genomic sequencing. Medical records were reviewed and families were interviewed to ascertain features at birth, length of survival, developmental milestones, and medical complications. RESULTS Seventy-four percent (26 of 35) of the affected male subjects over the age of 1 year are living (range, 1 to 27 years); 80% remain completely or partially ventilator-dependent. In the absence of significant hypoxia, cognitive development is normal, and the muscle disorder appears nonprogressive. Several patients have had other medical problems not previously reported to be associated with MTM1. These include pyloric stenosis (4 male subjects from 3 families), spherocytosis (2 patients), gallstones (4 patients), kidney stones or nephrocalcinosis (2 patients), a vitamin K responsive bleeding diathesis (2 patients), and height >/=90% for age (40% of the patients). Six patients have had biochemical evidence of liver dysfunction, and 2 patients died after significant liver hemorrhage. CONCLUSIONS These data suggest that the prognosis for X-linked MTM may not be as poor as previously reported. However, at least some long-term survivors appear at risk for medical complications involving other organ systems, and patients should be carefully monitored for these potentially life-threatening complications. The pleiotropic symptoms demonstrated in these patients strongly suggest that the function of the MTM1 protein is not limited to developing muscle cells.
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Affiliation(s)
- G E Herman
- Children's Hospital Research Foundation, Columbus, OH 43206, USA
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157
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Tanner SM, Schneider V, Thomas NS, Clarke A, Lazarou L, Liechti-Gallati S. Characterization of 34 novel and six known MTM1 gene mutations in 47 unrelated X-linked myotubular myopathy patients. Neuromuscul Disord 1999; 9:41-9. [PMID: 10063835 DOI: 10.1016/s0960-8966(98)00090-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
X-linked myotubular myopathy (XLMTM) is a congenital muscle disorder mainly affecting newborn males. Neonatal muscle weakness and hypotonia usually leads to a rapid demise. The responsible gene, MTM1, was isolated in 1996, and mutational data derived from 90 patients have been published. We report on our findings in a further 53 patients, using genomic DNA and mRNA screening protocols. Thirty-four novel mutations were identified in 37 cases, and six known mutations found in 10 other patients. The 34 new mutations include five large deletions, eight nonsense, six frameshift, five missense, and eight splice-site mutations, whereas two intronic variants causing partial exon skipping represent the first report on such a mechanism in MTM1. Two deletions, one involving exon 1, and the second exon 15, are the first defects to be identified in these exons. The heterogeneity of the mutations, their mutational origins, and the varied ethnic backgrounds of the patients, indicate that the majority of XLMTM families are affected by unique MTM1 mutations.
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Affiliation(s)
- S M Tanner
- Human Molecular Genetics, Department of Clinical Research, Children's Hospital, University of Berne, Switzerland.
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158
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Kioschis P, Wiemann S, Heiss NS, Francis F, Götz C, Poustka A, Taudien S, Platzer M, Wiehe T, Beckmann G, Weber J, Nordsiek G, Rosenthal A. Genomic organization of a 225-kb region in Xq28 containing the gene for X-linked myotubular myopathy (MTM1) and a related gene (MTMR1). Genomics 1998; 54:256-66. [PMID: 9828128 DOI: 10.1006/geno.1998.5560] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
MTM1 is responsible for X-linked recessive myotubular myopathy, which is a congenital muscle disorder linked to Xq28. MTM1 is highly conserved from yeast to humans. A number of related genes also exist. The MTM1 gene family contains a consensus sequence consisting of the active enzyme site of protein tyrosine phosphatases (PTPs), suggesting that they belong to a new family of PTPs. Database searches revealed homology of myotubularin and all related peptides to the cisplatin resistance-associated alpha protein, which implicates an as yet unknown function. In addition, homology to the Sbf1 protein (SET binding factor 1), involved in the oncogenic transformation of fibroblasts and differentiation of myoblasts, was also evident. We describe 225 kb of genomic sequence containing MTM1 and the related gene, MTMR1, which lies 20 kb distal to MTM1. Although there is only moderate conservation of the exons, the striking similarity in the gene structures indicates that these two genes arose by duplication. Calculations suggest that this event occurred early in evolution long before separation of the human and mouse lineages. So far, mutations have been identified in the coding sequence of only 65% of the patients analyzed, indicating that the remaining mutations may lie in noncoding regions of MTM1 or possibly in MTMR1. Knowledge of the genomic sequence will facilitate mutation analyses of the coding and noncoding sequences of MTM1 and MTMR1.
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Affiliation(s)
- P Kioschis
- Deutsches Krebsforschungszentrum, Molekulare Genomanalyse, Im Neuenheimer Feld 280, Heidelberg, 69120, Germany
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159
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The t(4;14) Translocation in Myeloma Dysregulates Both FGFR3and a Novel Gene, MMSET, Resulting in IgH/MMSET Hybrid Transcripts. Blood 1998. [DOI: 10.1182/blood.v92.9.3025] [Citation(s) in RCA: 392] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
Previously we reported that a karyotypically silent t(4;14)(p16.3;q32.3) translocation is present in about 25% of multiple myeloma (MM) tumors, and causes overexpression of FGFR3, which is 50 to 100 kb telomeric to the 4p16 breakpoints. Frequent FGFR3 kinase activating mutations in MM with t(4;14) translocations substantiate an oncogenic role for FGFR3. We now report that the 4p16 breakpoints occur telomeric to and within the 5′ introns of a novel gene,MMSET (Multiple Myeloma SETdomain). In normal tissues, MMSET has a complex pattern of expression with a short form (647 amino acids [aa]) containing an HMG box andhath region, and an alternatively spliced long form (1365 aa) containing the HMG box and hath region plus 4 PHD fingers and a SET domain. Although t(4;14) translocation results in IgH/MMSET hybrid transcripts, overexpression of MMSET also occurs from endogenous promoters on 4p16. Given the homology to HRX/MLL1/ALL1at 11q23 that is dysregulated by translocations in acute leukemia, we hypothesize that dysregulation of MMSET contributes to neoplastic transformation in MM with t(4;14) translocation. This is the first example of an IgH translocation that simultaneously dysregulates two genes with oncogenic potential: FGFR3 on der(14) andMMSET on der(4).
© 1998 by The American Society of Hematology.
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160
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The t(4;14) Translocation in Myeloma Dysregulates Both FGFR3and a Novel Gene, MMSET, Resulting in IgH/MMSET Hybrid Transcripts. Blood 1998. [DOI: 10.1182/blood.v92.9.3025.421k53_3025_3034] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previously we reported that a karyotypically silent t(4;14)(p16.3;q32.3) translocation is present in about 25% of multiple myeloma (MM) tumors, and causes overexpression of FGFR3, which is 50 to 100 kb telomeric to the 4p16 breakpoints. Frequent FGFR3 kinase activating mutations in MM with t(4;14) translocations substantiate an oncogenic role for FGFR3. We now report that the 4p16 breakpoints occur telomeric to and within the 5′ introns of a novel gene,MMSET (Multiple Myeloma SETdomain). In normal tissues, MMSET has a complex pattern of expression with a short form (647 amino acids [aa]) containing an HMG box andhath region, and an alternatively spliced long form (1365 aa) containing the HMG box and hath region plus 4 PHD fingers and a SET domain. Although t(4;14) translocation results in IgH/MMSET hybrid transcripts, overexpression of MMSET also occurs from endogenous promoters on 4p16. Given the homology to HRX/MLL1/ALL1at 11q23 that is dysregulated by translocations in acute leukemia, we hypothesize that dysregulation of MMSET contributes to neoplastic transformation in MM with t(4;14) translocation. This is the first example of an IgH translocation that simultaneously dysregulates two genes with oncogenic potential: FGFR3 on der(14) andMMSET on der(4).
© 1998 by The American Society of Hematology.
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161
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Wallgren-Pettersson C. 58th ENMC workshop: myotubular myopathy 20-22 March, 1998, Naarden, The Netherlands. Neuromuscul Disord 1998; 8:521-5. [PMID: 9829284 DOI: 10.1016/s0960-8966(98)00076-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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162
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Minassian BA, Lee JR, Herbrick JA, Huizenga J, Soder S, Mungall AJ, Dunham I, Gardner R, Fong CY, Carpenter S, Jardim L, Satishchandra P, Andermann E, Snead OC, Lopes-Cendes I, Tsui LC, Delgado-Escueta AV, Rouleau GA, Scherer SW. Mutations in a gene encoding a novel protein tyrosine phosphatase cause progressive myoclonus epilepsy. Nat Genet 1998; 20:171-4. [PMID: 9771710 DOI: 10.1038/2470] [Citation(s) in RCA: 325] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Lafora's disease (LD; OMIM 254780) is an autosomal recessive form of progressive myoclonus epilepsy characterized by seizures and cumulative neurological deterioration. Onset occurs during late childhood and usually results in death within ten years of the first symptoms. With few exceptions, patients follow a homogeneous clinical course despite the existence of genetic heterogeneity. Biopsy of various tissues, including brain, revealed characteristic polyglucosan inclusions called Lafora bodies, which suggested LD might be a generalized storage disease. Using a positional cloning approach, we have identified at chromosome 6q24 a novel gene, EPM2A, that encodes a protein with consensus amino acid sequence indicative of a protein tyrosine phosphatase (PTP). mRNA transcripts representing alternatively spliced forms of EPM2A were found in every tissue examined, including brain. Six distinct DNA sequence variations in EPM2A in nine families, and one homozygous microdeletion in another family, have been found to cosegregate with LD. These mutations are predicted to cause deleterious effects in the putative protein product, named laforin, resulting in LD.
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Affiliation(s)
- B A Minassian
- Department of Genetics, The Hospital for Sick Children, University of Toronto, Ontario, Canada
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163
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Laporte J, Blondeau F, Buj-Bello A, Tentler D, Kretz C, Dahl N, Mandel JL. Characterization of the myotubularin dual specificity phosphatase gene family from yeast to human. Hum Mol Genet 1998; 7:1703-12. [PMID: 9736772 DOI: 10.1093/hmg/7.11.1703] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
X-linked myotubular myopathy (XLMTM) is a severe congenital muscle disorder due to mutations in the MTM1 gene. The corresponding protein, myotubularin, contains the consensus active site of tyrosine phosphatases (PTP) but otherwise shows no homology to other phosphatases. Myotubularin is able to hydrolyze a synthetic analogue of tyrosine phosphate, in a reaction inhibited by orthovanadate, and was recently shown to act on both phosphotyrosine and phosphoserine. This gene is conserved down to yeast and strong homologies were found with human ESTs, thus defining a new dual specificity phosphatase (DSP) family. We report the presence of novel members of the MTM gene family in Schizosaccharomyces pombe, Caenorhabditis elegans, zebrafish, Drosophila, mouse and man. This represents the largest family of DSPs described to date. Eight MTM-related genes were found in the human genome and we determined the chromosomal localization and expression pattern for most of them. A subclass of the myotubularin homologues lacks a functional PTP active site. Missense mutations found in XLMTM patients affect residues conserved in a Drosophila homologue. Comparison of the various genes allowed construction of a phylogenetic tree and reveals conserved residues which may be essential for function. These genes may be good candidates for other genetic diseases.
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Affiliation(s)
- J Laporte
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, 1 rue Laurent Fries, BP 163, 67404 Illkirch Cedex, France
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164
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Isakoff SJ, Cardozo T, Andreev J, Li Z, Ferguson KM, Abagyan R, Lemmon MA, Aronheim A, Skolnik EY. Identification and analysis of PH domain-containing targets of phosphatidylinositol 3-kinase using a novel in vivo assay in yeast. EMBO J 1998; 17:5374-87. [PMID: 9736615 PMCID: PMC1170863 DOI: 10.1093/emboj/17.18.5374] [Citation(s) in RCA: 271] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Phosphatidylinositol 3-kinase (PI3K) mediates a variety of cellular responses by generating PtdIns(3,4)P2 and PtdIns(3,4,5)P3. These 3-phosphoinositides then function directly as second messengers to activate downstream signaling molecules by binding pleckstrin homology (PH) domains in these signaling molecules. We have established a novel assay in the yeast Saccharomyces cerevisiae to identify proteins that bind PtdIns(3,4)P2 and PtdIns(3,4,5)P3 in vivo which we have called TOPIS (Targets of PI3K Identification System). The assay uses a plasma membrane-targeted Ras to complement a temperature-sensitive CDC25 Ras exchange factor in yeast. Coexpression of PI3K and a fusion protein of activated Ras joined to a PH domain known to bind PtdIns(3,4)P2 (AKT) or PtdIns(3,4,5)P3 (BTK) rescues yeast growth at the non-permissive temperature of 37 degreesC. Using this assay, we have identified several amino acids in the beta1-beta2 region of PH domains that are critical for high affinity binding to PtdIns(3,4)P2 and/or PtdIns(3,4,5)P3, and we have proposed a structural model for how these PH domains might bind PI3K products with high affinity. From these data, we derived a consensus sequence which predicts high-affinity binding to PtdIns(3, 4)P2 and/or PtdIns(3,4,5)P3, and we have identified several new PH domain-containing proteins that bind PI3K products, including Gab1, Dos, myosinX, and Sbf1. Use of this assay to screen for novel cDNAs which rescue yeast at the non-permissive temperature should provide a powerful approach for uncovering additional targets of PI3K.
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Affiliation(s)
- S J Isakoff
- The Skirball Institute for Biomolecular Medicine and Department of Pharmacology, New York University Medical Center, New York, NY 10016, USA
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165
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De Vivo I, Cui X, Domen J, Cleary ML. Growth stimulation of primary B cell precursors by the anti-phosphatase Sbf1. Proc Natl Acad Sci U S A 1998; 95:9471-6. [PMID: 9689104 PMCID: PMC21362 DOI: 10.1073/pnas.95.16.9471] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/1998] [Indexed: 02/08/2023] Open
Abstract
SET binding factor 1 (Sbf1) was originally discovered by virtue of its interaction with a highly conserved motif (the SET domain) of unknown function in the protooncoprotein homolog of Drosophila trithorax, Hrx. Sbf1 shares extensive sequence similarity with myotubularin, a dual specificity phosphatase (dsPTPase) that is mutated in a subset of patients with inherited myopathies. Both Sbf1 and myotubularin interact with the SET domains of Hrx and other epigenetic regulatory proteins, but Sbf1 lacks phosphatase activity due to several evolutionarily conserved amino acid changes in its structurally preserved catalytic pocket. Thus, Sbf1 has features of an anti-phosphatase that could competitively antagonize dsPTPases; however the in vivo role for such factors remains unknown. Given its ability to physically interact with Hrx, a developmental regulator subject to translocation-induced mutations in B cell precursor leukemias, the current studies were undertaken to assess the effects of Sbf1 on lymphopoiesis. After infection with recombinant Sbf1 retroviruses, bone marrow cells were plated under Whitlock-Witte conditions for long-term culture of B lineage cells. Sbf1-expressing cells rapidly dominated the cultures resulting in clonal outgrowths of B cell progenitors that retained a dependence on their primary bone marrow-derived stroma for continuous growth in vitro. Structure/function analyses demonstrated that the SET interaction domain of Sbf1 was necessary and sufficient for growth alterations of B cell progenitors. These observations support a model in which Sbf1 functions as a SET domain-dependent positive regulator of growth-inducing kinase signaling pathways that impinge on SET domain proteins. SET domain-dsPTPase interactions appear to be critically important for regulating the growth properties of B cell progenitors.
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Affiliation(s)
- I De Vivo
- Department of Pathology, Stanford University Medical Center, Stanford, CA 94305, USA
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166
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Wishart MJ, Dixon JE. Gathering STYX: phosphatase-like form predicts functions for unique protein-interaction domains. Trends Biochem Sci 1998; 23:301-6. [PMID: 9757831 DOI: 10.1016/s0968-0004(98)01241-9] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The effects of tyrosine phosphorylation are manifested and regulated through protein domains that bind to specific phosphotyrosine motifs. STYX is a unique modular domain found within proteins implicated in mediating the effects of tyrosine phosphorylation in vivo. Individual STYX domains are not catalytically active; however, they resemble protein tyrosine phosphatase (PTP) domains and, like PTPs, contain core sequences that recognize phosphorylated substrates. Thus, the STYX domain adds to the repertoire of modular domains that can mediate intracellular signaling in response to protein phosphorylation.
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Affiliation(s)
- M J Wishart
- Dept of Physiology, University of Michigan, Ann Arbor 48109-0606, USA
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167
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Huang L, Ichimaru E, Pestonjamasp K, Cui X, Nakamura H, Lo GY, Lin FI, Luna EJ, Furthmayr H. Merlin differs from moesin in binding to F-actin and in its intra- and intermolecular interactions. Biochem Biophys Res Commun 1998; 248:548-53. [PMID: 9703963 DOI: 10.1006/bbrc.1998.9009] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The neurofibromatosis type 2 (NF2) tumor suppressor gene encodes merlin, a protein with homology to the cell membrane/F-actin linking proteins, moesin, ezrin and radixin. Unlike these closely related proteins, merlin lacks a C-terminal F-actin binding site detectable by actin blot overlays, and the GFP-tagged merlin C-terminal domain co-distributes with neither stress fibers nor cortical actin in NIH3T3 cells. Merlin also differs from the other three proteins in its inter- and intramolecular domain interactions, as shown by in vitro binding and yeast two-hybrid assays. As is true for ezrin, moesin and radixin, the N- and C-terminal domains of merlin type 1 bind to each other. However, full-length merlin and its N- and C-terminal domains, as well as the C-terminal domain of ezrin, interact with other full-length merlin type 1 molecules, and its C-terminal domain interacts with itself. Merlin 1 function in cells may thus depend on intra- and intermolecular interactions and their modulation, which include interactions with other members of this protein family.
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Affiliation(s)
- L Huang
- Department of Pathology, Stanford University School of Medicine, California 94305-5324, USA
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168
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Saha V, Young BD, Freemont PS. Translocations, fusion genes, and acute leukemia. J Cell Biochem 1998; 72 Suppl 30-31:264-276. [DOI: 10.1002/(sici)1097-4644(1998)72:30/31+<264::aid-jcb32>3.0.co;2-u] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/1998] [Accepted: 09/28/1998] [Indexed: 12/22/2022]
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