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H L Vos

Publications and source records attributed to H L Vos.

65 records · Page 4Linked to original sources
PubMed1992

Thrombospondin 3 (Thbs3), a new member of the thrombospondin gene family.

A third member of the thrombospondin gene family (Thbs3) has been partially characterized in the mouse. In both the mouse and humans, the Thbs3/THBS3 gene is located immediately upstream from the Muc1/MUC1 (episialin) gene; less than 3 kilobases separate the polyadenylation signal of one gene from the start of transcription of the other. The available coding sequence in Thbs3 shows a high degree of amino acid sequence identity to Thbs1 and Thbs2 (58 and 59%, respectively, in exons 15 and 16), but the exon/intron organization of Thbs3 appears to be more disparate than that of the two previously described members of the family. The shorter length of the Thbs3 mRNA (3.5 kilobases) can be attributed largely to a shorter 3'-untranslated region. The Thbs3 gene is expressed in a distinctive pattern in mouse tissues, with the highest level of expression in lung. This pattern suggests a unique function for the translation product of the Thbs3 gene.

Amino Acid Sequence↗
PubMed1992

Suppression of cellular aggregation by high levels of episialin.

Episialin is a mucin-like molecule located at the apical surface of most glandular epithelial cells. It is present at increased levels in carcinomas, where the molecule is often distributed over the entire cell surface. We have simulated this overproduction of episialin by transfecting a normal mammary epithelial cell line and a melanoma cell line with full-length complementary DNA encoding episialin. Transfectants of both cell lines containing episialin at levels similar to that of carcinoma cell lines do not aggregate as efficiently as their control cells, which do not express exogenous episialin. In mixing experiments, episialin transfectants are excluded from aggregates formed by these control cells, indicating that high levels of episialin on one of the interacting cells is sufficient to inhibit aggregation. The effect of episialin overexpression on aggregation is probably not only due to the negative charge of its numerous sialic acid residues, since neuraminidase treatment only partially restored the aggregation capacity of the transfectants. We propose that episialin, as a result of its large, extended, and rigid structure, can mask most cell surface molecules in its immediate surroundings and that a high density of episialin can severely disturb the interaction of cell surface proteins with macromolecules on adjacent cell membranes.

Breast↗
PubMed1992

Cell membrane-associated mucins and their adhesion-modulating property.

A class of highly sialylated glycoproteins with very large mucin-like domains that protrude high above the plasma membrane have been shown to strongly reduce cellular adhesion. In normal epithelial cells, where the expression is restricted to the luminal side of the cell, these molecules may prevent inadvertent closing of the lumen as a result of weak, non-specific protein-protein interactions between opposite luminal membranes. In malignant tumors cellular polarization is often lost, which can lead to the entire cell surface being covered by these molecules. The resulting strongly reduced adhesion and immune recognition properties may play an important role during invasion and metastasis.

Animals↗
PubMed1991

The mouse episialin (Muc1) gene and its promoter: rapid evolution of the repetitive domain in the protein.

We have cloned the Muc1 gene of the mouse, encoding the murine equivalent of human episialin (also known as EMA or PEM), a mucin-like glycoprotein that is overexpressed in carcinoma cells. The extracellular domain of the mouse protein, that mainly consists of tandem repeats, contains 16 repeats of variable length and sequence, whereas the human protein usually contains between 30 and 90 nearly identical repeats. The murine repeats contain more potential O-glycan side chains and this may result in a more extended conformation of the murine protein. The transmembrane and cytoplasmic domains of the protein show about 90% conservation. The promoter region shows many conserved regions that could function as transcription factor binding sites.

Amino Acid Sequence↗
PubMed1991

A single nucleotide polymorphism in an exon dictates allele dependent differential splicing of episialin mRNA.

The episialin gene (MUC1) encodes an epithelial mucin containing a variable number of repeats with a length of twenty amino acids, resulting in many different alleles that can be subdivided into two size classes. The episialin pre-mRNA uses either one of two neighbouring splice acceptor sites for exon 2, which mainly encodes the repeats. Using the genetic polymorphism of the episialin gene to identify different alleles, we show here that the splice site recognition is allele dependent and is based on a single A/G nucleotide difference in exon 2 eight nucleotides downstream of the second splice acceptor site. Transfection experiments confirm that this polymorphic nucleotide regulates the splice site selection. The identity of this nucleotide is in most cases correlated with one of the size classes of the alleles, indicating that mutations altering the number of repeats seldom arise by unequal cross-over between the repeat regions.

Alleles↗
PubMed1990

Episialin, a carcinoma-associated mucin, is generated by a polymorphic gene encoding splice variants with alternative amino termini.

Episialin is a mucin-type glycoprotein present at the luminal side of most glandular epithelial cells. We have isolated cDNA clones encoding episialin and determined the structure of the gene. The gene encodes a transmembrane protein which consists of, for the greater part, tandem repeats of 20 amino acids. The number of these repeats varies between 40 and 90 among different alleles. The repeats and most of the remainder of the protein are very rich in potential O-linked glycosylation sites. Two different splice variants were found. Interestingly, the proteins encoded by these two variants differ in their signal sequences and in the extreme amino-terminal parts of the mature proteins, suggesting alternative processing of these two species.

Amino Acid Sequence↗
PubMed1990

Physical mapping of two temperature-sensitive adenovirus mutants affected in the DNA polymerase and DNA binding protein.

We have determined the exact nature of two thermosensitive (ts) adenovirus mutants, H5ts19 and H5ts149, which map to different genes in the E2 transcription unit. The H5ts19 mutation appears to stem from a single base-pair change of A-T to G-C at position 1840 (numbering as in ref. 1), corresponding to codon 154 of the gene coding for DBP. This results in a glutamine-to-arginine change in the amino-terminal domain of the protein. H5ts19 is defective in a late stage of infection, during virus assembly. This phenotype strongly differs from that described for the limited number of known DBP mutants, indicating that DBP is not only functional during DNA replication, but also plays a role in the late phase of the infection cycle. The defect of the (N group) mutant H5ts149 affects the initiation of viral DNA replication. Marker rescue experiments followed by nucleotide sequence analysis of H5ts149 DNA revealed a single point mutation in the gene coding for the Ad pol. A transition of C-G to A-T at position 7563 (numbering as in ref. 2) changes amino acid residue 411 of Ad pol, a leucine residue, to phenylalanine. This mutation is located in a region conserved among various DNA polymerases, which suggests an important role of this domain in DNA replication.

Adenoviridae↗
PubMed1989

Characterization of adenovirus type 5 insertion and deletion mutants encoding altered DNA binding proteins.

We have introduced insertion and deletion mutations in the cloned DNA binding protein (DBP) gene of adenovirus type 5. The mutated DBP genes were subsequently introduced in the viral genome by a combination of in vitro and in vivo methods. The resulting mutant viruses were tested for their viability in human 293 cells and an initial characterization of these viruses was performed. Viable mutants with insertions in the carboxyl-terminal portion of the gene could not be obtained. In contrast, a number of viable mutants were constructed that contained insertions or deletions in the amino-terminal half of DBP. Several of these, which covered the region between amino acid (aa) residues 39 and 81, were phenotypically wild type, implying that this segment is completely dispensable for DBP function. However, mutations altering the region encompassed by aa 2-38 were, at least, partially defective suggesting that this region is important for full activity of the protein.

Adenoviruses, Human↗
PubMed1988

The binding of in vitro synthesized adenovirus DNA binding protein to single-stranded DNA is stimulated by zinc ions.

We have synthesized wild type DNA binding protein (DBP) of adenovirus type 5 (Ad5) and several truncated forms of this protein by a combination of in vitro transcription and translation. The proteins obtained were tested for binding to a single-stranded DNA-cellulose column. It could be shown that for binding of in vitro synthesized wild type DBP, it is necessary to add zinc ions to the in vitro translation system. Binding studies with the truncated proteins revealed that deletion of the carboxyl-terminal 46 amino acids abolishes DNA binding.

Adenoviruses, Human↗
PubMed1988

The genes encoding the DNA binding protein and the 23K protease of adenovirus types 40 and 41.

The adenovirus (Ad) single-stranded DNA binding protein (DBP) is a multifunctional protein. It is thought to consist of two domains, the amino-terminal domain involved in host-range determination and the carboxyl-terminal domain functioning in DNA replication and DNA binding. We have determined the nucleotide sequences of the DBP genes of Ad40 and Ad41, two human adenoviral serotypes that differ significantly from other adenoviruses. Regions of structural and functional importance in the corresponding proteins could be identified by comparison of the amino acid sequences with those of other known DBPs. In addition, the nucleotide sequences of the DBP early promoters, of the 23K protease genes, and of parts of the hexon and 100K protein genes have been determined. It can be deduced from the nucleotide sequences, that the Ad40 and Ad41 DBPs are relatively small (473 and 474 amino acids (a.a.), respectively, versus 529 a.a. for the Ad5 DBP). This is caused by the presence of very small amino-terminal domains of 119 a.a. (Ad40) and 120 a.a. (Ad41), as compared to 173 a.a. for the corresponding Ad5 domain. Only a few amino acids in this domain have been conserved in all known DBPs. The carboxyl-terminal domains show a higher degree of sequence conservation. In this domain, four strongly conserved regions can be identified, one of which might form a metal-binding site. The 23K proteases of both Ad40 and Ad41 show a strong homology to the Ad2 and Ad5 proteins, with the exception of the carboxyl-terminal end of the proteins. The 23K protease gene of Ad41 has an open reading frame that extends beyond the polyadenylation signal, in contrast to the Ad40 gene that ends well in front of the signal.

Adenoviruses, Human↗