Biomedical subjects

E C Zwarthoff

Publications and source records attributed to E C Zwarthoff.

65 records · Page 4Linked to original sources

PubMed1989

Differential expression of interferon alpha and beta induced with Newcastle disease virus in mouse macrophage cultures.

Stimulation of mouse macrophages with Newcastle disease virus (NDV) leads to a rapid and high interferon (IFN) response. The magnitude of this response is influenced by the mouse genotype. We have analysed NDV-induced IFN production at the protein and mRNA levels in two different populations of macrophages derived from 'high producer' C57BL/6 and 'low producer' BALB/c mice in vitro. The data indicate that bone marrow and peritoneal macrophages from both strains grown in the presence of L cell conditioned medium (CM) as a source of macrophage colony-stimulating factor 1 (M-CSF) or purified murine M-CSF produce 10- to 50-fold more IFN on a per cell basis than cultures of resident peritoneal macrophages. These differences were also found when steady state levels of IFN mRNA were analysed. Differential analysis for the ratios of IFN-alpha and IFN-beta showed that CM- or M-CSF-cultured macrophages produced equal amounts of both IFN species as determined by specific monoclonal antibodies and hybridization experiments using IFN-alpha and IFN-beta DNA probes, whereas resident peritoneal macrophages induced under identical conditions produced almost exclusively IFN-beta. This suggests a stimulating effect of M-CSF on IFN synthesis in NDV-induced cultures of mouse macrophages, which is in part due to additional activation of IFN-alpha gene expression.

2',5'-Oligoadenylate Synthetase↗

PubMed1988

Interferon expression in the testes of transgenic mice leads to sterility.

A plasmid containing the mouse interferon-alpha 1 gene under control of the mouse metallothionein-I promoter was used for the construction of transgenic mice. Four transgenic mice (two males and two females) were obtained containing 1 to over 10 copies of the introduced DNA. Both males appeared to be sterile. One of the female mice founded a transgenic strain in which the foreign DNA was transmitted to her offspring in a Mendelian fashion. In this strain most male animals are sterile or turn sterile with time. Northern blot analysis of several tissues of these animals shows that expression of the introduced interferon gene occurs only in the testis. In some of the animals biologically active interferon could also be detected in testes homogenates. Histological examination of testis tissue shows an ongoing degeneration of spermatogenic cells leading to calcium deposits and complete atrophy of the seminiferous tubules.

Animals↗

PubMed1988

Interferon-alpha-(IFN) producing CHO cell lines are resistant to the antiproliferative activity of IFN: a correlation with gene expression.

CHO cell lines that constitutively produce the murine interferon-alpha (IFN-alpha) subspecies alpha 4 and alpha 6 were constructed. The producer cell lines were protected against viral (vesicular stomatitis virus) infection by the IFN species secreted, but were resistant to the growth inhibitory activity of the IFN species. As compared with alpha 4, the alpha 6 protein displayed a high antiproliferative activity when added to normal CHO cells, which correlates completely with the high antiviral activity of alpha 6 on these cells. Three messenger ribonucleic acid (mRNA) species, which are normally induced in CHO cells by IFN treatment (1-8, 2-5A synthetase, and ISG 15) were constitutively present in CHO producer cell lines. The level of another mRNA (ISG 54), however, was very low in the producer cells as compared with its expression in short-term IFN-treated cells. These data indicate that 1-8, 2-5A synthetase and ISG 15 are not involved in the antigrowth activity of IFN in this system, but rather suggest a function of ISG 54 in this respect.

Animals↗

PubMed1988

Structure-function analysis of murine interferon-alpha: antiviral properties of novel hybrid interferons.

As described earlier the protein products of the murine interferon (IFN) genes MuIFN-alpha 1, -alpha 2, and -alpha 4 differ in their antiviral activity on hamster (CHO) and mouse (L929) cells. For structure-function analysis, hybrids were prepared between the three genes using common restriction enzyme sites. Natural and hybrid genes were transiently expressed in monkey COS cells. Under the conditions used IFN constituted 20-30% of the total amount of secreted proteins. Using a panel of hybrids either between alpha 1 and alpha 2 or between alpha 1, alpha 2, and alpha 4, the amino-terminal region of the protein, from amino acids 10 to 58, was found to determine its antiviral activity on hamster cells. On mouse cells, the antiviral activities of hybrids between alpha 4 and either alpha 1 or alpha 2 were compared. The high activity of alpha 4 (five to ten times that of alpha 1 or alpha 2) was not transmitted to hybrids having the amino-terminal part of alpha 4, but coincided with the presence of the alpha 4 carboxy-terminal region in all but one hybrid construct. The deletion of five amino acids (positions 103-107) located in this region of alpha 4 did not affect antiviral activity when introduced into MuIFN-alpha 2 and a MuIFN-alpha 42 hybrid by site-directed mutagenesis.

Animals↗

PubMed1988

Structure-function analysis of mouse interferon alpha species: MuIFN-alpha 10, a subspecies with low antiviral activity.

A mouse interferon alpha gene (MuIFN-alpha 10) was isolated from a BALB/c cosmid genomic library. The gene was located on a 1.8 kb HindIII fragment and a 5.1 kb EcoRI fragment. The coding region and parts of the 5' and 3' non-coding regions were sequenced. The results showed that the MuIFN-alpha 10 gene encoded a protein of 167 amino acids. Like most other MuIFN-alpha species it contained a putative N-glycosylation site at amino acid positions 78 to 80. It also possessed cysteine residues at positions 1, 29, 86, 99 and 129. In the signal peptide, in addition to cysteine 21, which is present in all MuIFN-alpha species sequenced so far, a cysteine was found at position 22. At the amino acid level MuIFN-alpha 10 showed strong homology to MuIFN-alpha 1 (only 15 out of 167 amino acids were different). The MuIFN-alpha 10 gene was transiently expressed in monkey COS cells under the direction of the simian virus 40 early promoter. The protein product secreted by COS cells was equally active on mouse (L929) and hamster (CHO) cells. However, as compared to MuIFN-alpha 1 and MuIFN-alpha 4 the specific activity on mouse cells of the protein was 10- to 100-fold lower. To find out which region of its structure was responsible for this low activity, hybrids of the genes encoding MuIFN-alpha 10 and MuIFN-alpha 1 were constructed using the two common XmmI sites which correspond to positions between amino acids 67 and 68 and 123 and 124, respectively. The data showed that hybrid constructs which were MuIFN-alpha 1-like from amino acid 68 or MuIFN-alpha 10-like from position 124 to the C terminus possessed high antiviral activity. Other hybrid constructs were hardly active at all. This implied that the amino acid 68 to 123 region was mainly responsible for the low antiviral activity of MuIFN-alpha 10. In this part of the molecule MuIFN-alpha 1 and MuIFN-alpha 10 differed in only five amino acids. A serine at position 110 and a valine at 85 were unique to MuIFN-alpha 10 as compared to all known MuIFN-alpha and human IFN-alpha subspecies.

Amino Acid Sequence↗

PubMed1987

Two domains in alpha interferons influence the efficacy of the antiviral response.

Murine interferon-alpha 1 and murine interferon-alpha 4 share 80% of their amino acids, yet the proteins differ considerably in their ability to protect mouse or hamster cells against viral infection. With the aim of localizing areas within these proteins which influence the biological response we have constructed hybrid alpha 1 alpha 4 genes by means of homologous recombination of the parent genes. When the antiviral activities of these proteins were compared, it appeared that there are at least two domains that affect the biological response to these proteins: area A (amino acids 10-20) and area B (amino acids 55-67). These areas are presumably involved in the interaction between ligand and receptor. Most interestingly, hybrids in which area A from IFN-alpha 1 is combined with area B from alpha 4, have antiviral activities on homologous cells that are one to two orders of magnitude higher than those of the parent proteins.

Amino Acid Sequence↗

PubMed1986

Transient expression of murine interferon-alpha genes in mouse and monkey cells.

The coding regions of murine interferon-alpha (IFN-alpha) genes were combined with promoter and 3'-noncoding sequences from other eukaryotic genes. Transient expression of these fusion genes was achieved in monkey COS cells and in a mouse cell line (TOP cells) expressing polyoma virus (Py) large T antigen constitutively. The efficiency of the different expression plasmids was determined by measuring the amount of IFN secreted into the medium. Replacement of the 3'-noncoding region of an IFN-alpha gene by that of the rabbit beta-globin gene resulted in a fourfold higher IFN-alpha production. The SV40 early promoter and the Moloney murine leukemia virus (MoMLV) long terminal repeat (LTR) produced similar amounts of IFN-alpha in COS cells. However, a tandem combination of the SV40 enhancer/early promoter and the mouse metallothionein-I promoter appeared fivefold more active than the SV40 early promoter. In TOP cells the MoMLV LTR was found to be threefold more active than the Py early promoter.

Animals↗

PubMed1986

Properties of natural and hybrid murine alpha interferons.

Four natural murine interferon-alpha genes (MuIFN-alpha 1, -alpha 2, -alpha 4 and -alpha 6) and four hybrid genes (alpha 1 alpha 4, alpha 2 alpha 4, alpha 4 alpha 1 and alpha 4 alpha 2) were transiently expressed in monkey COS cells under the transcriptional control of the simian virus 40 early promoter. The proteins were labelled with [35S]methionine during a 16 h incubation and proteins secreted by the cells during this period were separated by polyacrylamide gel electrophoresis and subsequently visualized by fluorography. Under the conditions used, the IFNs represented 5 to 10% of the total amount of secreted proteins. All genes were found to encode biologically active IFN subspecies, including alpha 4 which has a deletion of five amino acids. When the specific activities of the proteins were compared, it appeared that the specific antiviral activity of alpha 4 on mouse cells was three- to sixfold higher than the activities of the other natural IFN subspecies. The specific activities of the hybrid proteins were similar to those of the natural proteins, except for the alpha 2 alpha 4 hybrid which had a higher specific activity than the original proteins. The ability of the natural and hybrid subspecies to protect hamster cells against viral infection was determined using MuIFN-alpha 1 as a standard. Large differences in activity were found, with alpha 6 as the most and alpha 4 as the least active subspecies.

Animals↗

PubMed1985

Organization, structure and expression of murine interferon alpha genes.

Using a human interferon-alpha probe we have isolated recombinant phages containing murine interferon-alpha (Mu IFN-alpha) genes from a genomic library. One of these phages contained two complete Mu IFN-alpha genes and part of a third gene. The insert of a second phage held two IFN genes. This indicates that the Mu IFN-alpha genes are clustered in the genome as is the case for the analogous human genes. The nucleotide sequences of these 5 genes were determined. They show that the genes are all different, albeit highly homologous. The deduced amino acid sequences show that four of the five genes contain a putative glycosylation site. Three genes were transiently expressed in COS cells and they gave rise to protein products showing antiviral properties. The expression of the five Mu IFN-alpha genes and the Mu IFN-beta gene was studied in virus-induced mouse L cells. The individual mRNAs were visualized in a nuclease S1 experiment, using a specific probe for each gene. In RNA preparations from induced cells mRNAs for each of the five alpha genes and the beta gene were present. However, substantial differences in the amounts of the individual mRNAs were observed.

Animals↗

PubMed1985

Mouse interferon alpha and beta genes are linked at the centromere proximal region of chromosome 4.

In order to determine the chromosomal localization of the murine interferon-alpha (MuIFN-alpha) and murine interferon-beta (MuIFN-beta) genes the DNAs of a panel of somatic cell hybrids were analysed by Southern blot hybridization. The hybrid cells were derived from E36 Chinese hamster cells and GRSL or GR MaTu mouse cells and retained all hamster chromosomes but segregated mouse chromosomes. The MuIFN-alpha probe used was a 0.7 kb HindIII-EcoRI fragment derived from the MuIFN-alpha 1 gene which hybridized with both mouse and hamster DNA. However, four fragments present in EcoRI digests of mouse DNA were clearly absent from the hybridization profile of EcoRI-digested hamster DNA and could be used for detection of MuIFN-alpha sequences in the hybrid cells. The MuIFN-beta probe, a 0.5 kb BglII-BamHI fragment derived from the MuIFN-beta gene, hybridized with a 2.6 kb EcoRI fragment of mouse DNA and only weakly cross-hybridized with a 4.8 kb EcoRI fragment in hamster DNA. Southern blot analysis of DNA from mouse/hamster hybrids compared with the analysis of chromosome markers showed that both the MuIFN-alpha and the MuIFN-beta genes are located on chromosome 4. Analysis of DNA from hybrids that contained only part of chromosome 4 indicated that the MuIFN-alpha gene family and the MuIFN-beta gene are situated at the centromere-proximal region of the chromosome.

Animals↗

PubMed1985

Constitutive expression of a murine interferon alpha gene in hamster cells and characterization of its protein product.

The coding part of a murine interferon alpha (MuIFN-alpha) gene was cloned into an expression plasmid containing the simian virus 40 early promoter and the rabbit beta-globin polyadenylation signal. This construct was transfected into Chinese hamster ovary cells, together with a plasmid containing the Ecogpt gene as a selection marker. Resulting colonies were assayed for constitutive interferon production and analysed for integration of MuIFN-alpha genes. There was no obvious correlation between the number of genes integrated and the amount of interferon produced. The highest producer, designated CHO-pSV10EF-3, contained four copies of the mouse gene and constitutively secreted up to 100 000 International Units of interferon per ml per day. The MuIFN-alpha subspecies produced by this clone was characterized by analysis of its antiviral activity on heterologous cells, heparin-Sepharose affinity chromatography and chromatofocusing. The results obtained indicate that it is identical or closely related to a minor component present in conventional MuIFN-alpha preparations.

Animals↗