Structure, Chromosomal Location, and Expression Profile of EXTR1 and EXTR2, New Members of the Multiple Exostoses Gene Family

Seki, Naohiko; Yamauchi, Masatake; Tsuji, Satsuki; Hayashi, Akiko; Kozuma, Sumie; Hori, Tada-aki

doi:10.1006/bbrc.1997.8062

Cited by 51 publications

(35 citation statements)

References 20 publications

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“…Both EXTL1 and EXTL3 have been shown to be able to transfer GlcNAc (but not GlcA) to K5 oligosaccharide acceptors and are likely to be involved in HS biosynthesis (14). Of the two, only EXTL3 is ubiquitously expressed in human tissues (27,28) and therefore more likely to be part of a universal HS chain-elongating complex. The more restricted mRNA expression of EXTL1 may indicate a more specialized role for this enzyme.…”

Section: Figmentioning

confidence: 99%

In Vitro Polymerization of Heparan Sulfate Backbone by the EXT Proteins

Busse

Kusche-Gullberg

2003

Journal of Biological Chemistry

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Multiple exosotoses is a dominantly inherited bone disorder caused by defects in EXT1 and EXT2, genes encoding glycosyltransferases involved in heparan sulfate chain elongation. Heparan sulfate polymerization occurs by the alternating addition of glucuronic acid and N-acetylglucosamine units to the nonreducing end of the polysaccharide. EXT1 and EXT2 are suggested to be dual glucuronyl/N-acetylglucosaminyltransferases, and a heterooligomeric complex of EXT1 and EXT2 (EXT1/2) is considered to be the biological functional polymerization unit. Here, we have investigated the in vitro polymerization capacities of recombinant soluble EXT1, EXT2, and EXT1/2 complex on exogenous oligosaccharide acceptors derived from Escherichia coli K5 capsular polysaccharide. Incubations of recombinant EXT1 or EXT1/2 complex with 3 H-labeled oligosaccharide acceptors and the appropriate nucleotide sugars resulted in conversion of the acceptors to higher molecular weight compounds but with different efficacies for EXT1 and EXT1/2. In contrast, incubations with recombinant EXT2 resulted in the addition of a single glucuronic acid but no further polymerization. These results indicate that EXT1 alone and the EXT1/2 heterocomplex can act as heparan sulfate polymerases in vitro without the addition of additional auxiliary proteins.

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Section: Figmentioning

confidence: 99%

In Vitro Polymerization of Heparan Sulfate Backbone by the EXT Proteins

Busse

Kusche-Gullberg

2003

Journal of Biological Chemistry

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“…However, three EXT-like genes homologous to EXT genes have been isolated: EXTL1, EXTL2͞EXTR2, and EXTL3͞ EXTR1 (20)(21)(22)(23). Their chromosomal locations imply that they also might be tumor suppressors (20,21,24,25), although they are not linked with HME.…”

Section: H Eparan Sulfate (Hs) Is a Glycosaminoglycan (Gag) Foundmentioning

confidence: 99%

Human tumor suppressor EXT gene family members EXTL1 and EXTL3 encode α1,4- N -acetylglucosaminyltransferases that likely are involved in heparan sulfate/ heparin biosynthesis

Kim

Kitagawa

Tamura

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

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157

144

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The tumor suppressors EXT1 and EXT2 are associated with hereditary multiple exostoses and encode bifunctional glycosyltransferases essential for chain polymerization of heparan sulfate (HS) and its analog, heparin (Hep). Three highly homologous EXT-like genes, EXTL1-EXTL3, have been cloned, and EXTL2 is an ␣1,4-GlcNAc transferase I, the key enzyme that initiates the HS͞Hep synthesis. In the present study, truncated forms of EXTL1 and EXTL3, lacking the putative NH 2-terminal transmembrane and cytoplasmic domains, were transiently expressed in COS-1 cells and found to harbor ␣-GlcNAc transferase activity. EXTL3 used not only N-acetylheparosan oligosaccharides that represent growing HS chains but also GlcA␤1-3Gal␤1-O-C 2H4NH-benzyloxycarbonyl (Cbz), a synthetic substrate for ␣-GlcNAc transferase I that determines and initiates HS͞Hep synthesis. In contrast, EXTL1 used only the former acceptor. Neither EXTL1 nor EXTL3 showed any glucuronyltransferase activity as examined with N-acetylheparosan oligosaccharides. Heparitinase I digestion of each transferase-reaction product showed that GlcNAc had been transferred exclusively through an ␣1,4-configuration. Hence, EXTL3 most likely is involved in both chain initiation and elongation, whereas EXTL1 possibly is involved only in the chain elongation of HS and, maybe, Hep as well. Thus, their acceptor specificities of the five family members are overlapping but distinct from each other, except for EXT1 and EXT2 with the same specificity. It now has been clarified that all of the five cloned human EXT gene family proteins harbor glycosyltransferase activities, which probably contribute to the synthesis of HS and Hep.

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“…The gene-specific PCR primers were designed within the coding region of the gene (5Ј-GAC AAA CCC AGC CAA GTG ACC-3Ј, 5Ј-GCG CAC ATC GGA GTT CGT TTC-3Ј, with the PCR product size 82 bp). PCR was carried out in the same manner as that described in previous reports (Seki et al 1997;Saito et al 1998). …”

Section: Chromosome Mappingmentioning

confidence: 99%

Isolation, tissue expression, and chromosomal assignment of a human LIM protein gene, showing homology to rat Enigma homologue (ENH)

Ueki

Seki²,

Yano

et al. 1999

J Hum Genet

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Rat ENH (Enigma homolog) is a LIM domain protein that associates with protein kinase C in an isoformspecific manner. We have identified a human cDNA which shares a significant sequence homology with rat ENH. The isolated cDNA clone, designated human ENH (hENH), was 3287 bp in length and encoded a predicted protein of 596 amino acids which had 88% overall identity to rat ENH protein. Northern blot analysis revealed that 1.9 kb of the hENH messenger RNA was predominantly expressed in heart and skeletal muscle, while 5.6 kb of the hENH messenger RNA was ubiquitously expressed in various human tissues. The chromosomal location of the gene was determined on chromosome 4q22 region, between markers WI-2900 and WI-3273, by polymerase chain reaction (PCR)-based analyses using both a human/rodent monochromosomal hybrid cell panel and a radiation hybrid mapping panel.

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Structure, Chromosomal Location, and Expression Profile of EXTR1 and EXTR2, New Members of the Multiple Exostoses Gene Family

Cited by 51 publications

References 20 publications

In Vitro Polymerization of Heparan Sulfate Backbone by the EXT Proteins

In Vitro Polymerization of Heparan Sulfate Backbone by the EXT Proteins

Human tumor suppressor EXT gene family members EXTL1 and EXTL3 encode α1,4- N -acetylglucosaminyltransferases that likely are involved in heparan sulfate/ heparin biosynthesis

Isolation, tissue expression, and chromosomal assignment of a human LIM protein gene, showing homology to rat Enigma homologue (ENH)

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