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M K Oskarsson

Publications and source records attributed to M K Oskarsson.

14 recordsLinked to original sources
PubMed1998

Proteolytic inactivation of MAP-kinase-kinase by anthrax lethal factor.

Anthrax lethal toxin, produced by the bacterium Bacillus anthracis, is the major cause of death in animals infected with anthrax. One component of this toxin, lethal factor (LF), is suspected to be a metalloprotease, but no physiological substrates have been identified. Here it is shown that LF is a protease that cleaves the amino terminus of mitogen-activated protein kinase kinases 1 and 2 (MAPKK1 and MAPKK2) and that this cleavage inactivates MAPKK1 and inhibits the MAPK signal transduction pathway. The identification of a cleavage site for LF may facilitate the development of LF inhibitors.

Animals↗
PubMed1988

Chicken homolog of the mos proto-oncogene.

We compared the sequence and properties of the chicken mos homolog with the previously characterized mouse and human c-mos genes. Sequence analysis revealed one major open reading frame of 1,047 base pairs encoding a protein of 349 amino acids. Both the nucleotide sequence and the deduced amino acid sequence showed 62% overall homology to mouse and human c-mos, but regions of higher conservation (approximately 70%) occurred in the putative ATP-binding and kinase domains. We detected mos transcripts by Northern (RNA) analyses in RNA prepared from chicken and quail ovaries and testes. Evidence for low levels of mos RNA expression in adult chicken heart, kidney, and spleen and in the entire embryo was obtained by S1 nuclease protection experiments. In contrast to the low transforming efficiency of human c-mos when linked to a mouse retroviral long terminal repeat element, chicken c-mos transformed NIH 3T3 cells as efficiently as mouse c-mos did. We also show that chicken primary embryo fibroblasts were morphologically altered when infected with an avian retroviral vector containing the chicken c-mos coding region.

Amino Acid Sequence↗
PubMed1988

Genetic analysis and developmental regulation of testis-specific RNA expression of Mos, Abl, actin and Hox-1.4.

The pattern of Mos proto-oncogene RNA expression in the gonads of the sterile mouse mutants, dominant spotting (W), sex reversal (Sxr), testicular feminization (Tfm), hypogonadal (hpg), quaking (qk), two t-haplotypes, three X-autosomal translocations, and the YPOS strain, is consistent with its presence in haploid spermatids in the testes and in oocytes in the ovaries. In the male-sterile mouse mutants the pattern of expression of the testis-specific transcripts for Abl, actin, and the mouse homeobox Hox-1.4 genes is identical to that observed for Mos. However, during the postnatal onset of normal spermatogenesis we detected differences in the time of the appearance of the four transcripts. We detected Hox-1.4 transcripts at day 20, Mos at day 25, and Abl and actin at day 30, demonstrating a specific regulation of expression of each of these genes during haploid spermatid maturation in the mouse. Furthermore, comparison of Mos, Abl and actin RNA expression in mouse and rat testes revealed species-specific variations in the regulation of gene expression.

Actins↗
PubMed1987

Defects in lens fiber differentiation are linked to c-mos overexpression in transgenic mice.

We describe three strains of transgenic mice derived by embryo microinjection of DNA consisting of a long terminal repeat (LTR) of Moloney murine sarcoma virus (Mo-MSV) linked to the murine c-mos coding sequences. Southern analysis of the genomic DNA of these strains suggested that in each case the transgene had integrated at a different chromosomal location. The strains were characterized by dominant changes in secondary lens fiber differentiation. Shortly after birth, insufficient elongation of differentiating lens fibers and lack of basement membrane secretion resulted in breakdown of the posterior lens capsule. This, in turn led to posterior protrusion and swelling of lens tissue. In the course of the first 3 weeks after birth, globular lens cells began to fill the entire anterior and posterior chambers of the eye. Concomitantly, there was massive overexpression of c-mos RNA in the lens. Whereas this construct has high transforming activity when transfected into NIH-3T3 cells, no hyperplasia or neoplasia have been observed in the affected lenses. Increased expression of c-mos RNA was not confined to the lens of the eye but has been detected in any of several tissues tested.

Animals↗
PubMed1986

Analysis of the transforming potential of the human homolog of mos.

The human homolog, c-moshu, of the mouse cellular mos proto-oncogene (c-mosmu) transforms NIH 3T3 cells at low efficiency. Furthermore, the c-moshu-induced foci are less distinct, and transformed cells contain a high level of human mos protein. The transforming activity of hybrid mos genes derived from human and mouse sequences reveals three domains within the coding region, as well as a negative regulatory sequence upstream from the c-moshu ORF that reduces its transforming efficiency. The mos C-terminal region, however, which contains the src-kinase homology domain, appears to have the greatest influence on transforming efficiency. The low transforming efficiency of c-moshu may provide a selective advantage to the host, but it also may indicate a reduced or modified function of mos in humans.

Animals↗
PubMed1984

Characterization of human transforming genes from chemically transformed, teratocarcinoma, and pancreatic carcinoma cell lines.

Dominant transforming genes that were transferred to mouse NIH3T3 cells by cellular DNAs prepared from a chemically transformed human cell line (MNNG-HOS), a human teratocarcinoma cell line (PA1), and a human pancreatic carcinoma cell line (A1165) were characterized (a) analyzing the repetitive human DNA sequences that were associated with the transforming gene and (b) determining their relationship to the oncogenes of the Harvey (rasH) and Kirsten (rasK) sarcoma viruses and to the human neuroblastoma transforming gene (rasN). The results show that the transforming gene activated in the teratocarcinoma cell line is identical to the neuroblastoma transforming gene and that the transforming gene of the pancreatic carcinoma cell line is a human homologue of rasK. In contrast, the transforming gene activated in the chemically transformed human cell line showed no detectable homology to rasK, rasH, and rasN.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1983

Tumorigenesis by transected cells in nude mice: a new method for detecting cellular transforming genes.

We have demonstrated that NIH 3T3 cells freshly transfected with either a cloned retroviral provirus or cell DNA derived from virally-transformed cells are able to induce tumors when injected subcutaneously into nude mice. Furthermore, cells transfected with DNA derived from at least three transformed human cell lines are able to induce tumors. These latter tumors contain human DNA sequences and DNA isolated from at least some of them is able to induce both foci and tumors in subsequent DNA transfection. Our data suggests that tumor induction by transfected 3T3 cells could serve as a powerful system for the selection of cells transformed by dominant cellular oncogenes. This method oviates the requirement that oncogenes induce clearly defined morphologically-transformed foci in order to be detected, and eliminates the need to maintain morphologically normal cells in tissue culture for many weeks, as well as the necessity of microscopically screning large numbers of tissue culture dishes. The tumors which arise in nude mice grow progressively, have been readily transplantable to other nude mice, and have been readily explantable into tissue culture. In addition, both DNA and RNA can be isolated directly from the mouse tumors to screen for the presence and expression of transfected sequences. We are currently examining other DNA samples from both human tumor-derived cell lines and primary human tumors to determine if this assay will detect and identify additional oncogenes. We are also studying the suitability of other normal cell lines as recipients in this assay, since cell lines which do not show readily discernible morphological transformation in monolayer culture may be suitable as tumor inducers following transfection. This assay should provide a convenient alternative method for detecting transforming genes and may help to increase the number of such sequence which can be identified and analyzed.

Animals↗
PubMed1982

New method for detecting cellular transforming genes.

Tumor induction in athymic nude mice can be used to detect dominant transforming genes in cellular DNA. Mouse NIH 3T3 cells freshly transfected with either cloned Moloney sarcoma proviral DNA or cellular DNA's derived from virally transformed cells induced tumors when injected into athymic nu/nu mice. Tumors were also induced by cells transfected with DNA from two tumor-derived and one chemically transformed human cell lines. The mouse tumors induced by human cell line DNA's contained human DNA sequences, and DNA derived from these tumors was capable of inducing both tumors and foci on subsequent transfection. Tumor induction in nude mice represents a useful new method for the detection and selection of cells transformed by cellular oncogenes.

Animals↗
PubMed1980

Biological activity of cloned Moloney sarcoma virus DNA: Terminally redundant sequences may enhance transformation efficiency.

We have measured the ability of cloned restriction fragments containing the whole and partial genomes of two strains of Moloney murine sarcoma virus to induce cell transformation in DNA transfection assays. The cloned intact ml and HTl murine sarcoma virus proviruses transform with an efficiency of approximately 40,000-50,000 focus-forming units/pmol of proviral DNA, and the majority of these transformed cells contain a rescuable viral genome. A cloned 2.1-kilobase-pair internal fragment of the murine sarcoma virus containing 1.2 kilobase pairs of sarcoma virus-specific sequences (src) and approximately 900 base pairs of leukemia virus-derived sequences adjacent to the 5' end of src transforms with approximately 1/10,000th the efficiency of the intact genome. When leukemia virus-deprived sequences containing a single copy of the 600-base-pair direct terminal repeated sequences are present at either the 5' or 3' end of this src-containing fragment, the transforming activity is stimulated 1000-fold. Cotransfection with a mixture of cloned fragments, one containing the internal 2.1-kilobase-pair src fragment and the other containing a single copy of the terminally redundant sequence, results in a 300-fold increase in transformation efficiency.

Animals↗
PubMed1978

Chemical determination of the m1 Moloney sarcoma virus pP60gag gene order: evidence for unique peptides in the carboxy terminus of the polyprotein.

The gene order of the ml Moloney sarcoma virus (mlMSV) specific pP60gag (P60) was determined by direct chemical analysis of the polyprotein. P60 was cleaved with cyanogen bromide (CNBr) into eight partial and complete fragments ranging in mass from 10,000 daltons to 58,000 daltons. Peptide maps of these fragments were compared to maps of p15, p12, and three CNBr fragments of p30. The polarity of p15 and p12 in a CNBr fragment of P60 was determined by carboxypeptidase A digestion; likewise the CNBr fragments of p30 were ordered by aminopeptidase digestion. The linear arrangement of P60 CNBr fragments gave the gene order of NH2-p15-p12-p30-COOH. The m3 isolate of MSV expresses a P70 gag polyprotein. Peptide maps of 48,000-dalton CNBr fragments of m3 P70 and ml P60 were similar and suggested that both polyproteins were similar through the NH2-terminal two-thirds of p30. However, the presence of peptides unique to the 10,500-dalton COOH-terminal fragment of m1MSV p30 and not present in the p30 of either m3MSV or Moloney leukemia virus suggested that the gag gene deletion in the m1 isolate begins in the p30 reading frame.

Cyanogen Bromide↗
PubMed1977

Cells transformed by certain strains of Moloney sarcoma virus contain murine p60.

It was previously demonstrated that the 60,000 dalton (p60) precursor-like polyprotein containing murine p30 was a constituent of the feline leukemia virus pseudotype of Moloney sarcoma virus [m1MSV(FeLV)]. It is now shown that p60 is detected in cells of five mammalian species transformed by m1MSV, indicating that p60 is specified by this genome. Moreover, little or no murine p30 is detected in the m1MSV-transformed cells, suggesting that the murine group p30 antigenic reactivity of S + L- cells is ude to p60. Pulse-chase studies in cells producing m1MSV(FeLV) show that p60 is the largest polypeptide detectable during the pulse, and that intracellular p60 is not cleaved into smaller (for example, p30) polypeptides during chase periods of up to 10 hr. The lack of cleavage of p60 is in contrast to the properties of p30 precursors detected in cells containing replicating avian or mammalian RNA tumor viruses. The inefficient cleavage of intracellular p60 and the kinetics of appearance of murine p30 in extracellular m1MSV(FeLV) suggest that p60 cleavage to p30 occurs in cells shortly before virus release. While only p60 was detected in the m1MSV-transformed cells, p60 and p70 were detected in m3MSV-transformed cells, and no immunoprecipitable polypeptides were detected in HT-1 MSV-transformed cells. The observed differences in the intracellular polypeptide expression by each of the strains of MSV suggests differences in genetic content.

Cell Line↗
PubMed1977

Phosphorylation and nucleic acid binding properties of m1 Moloney murine sarcoma virus-specific pP60gag.

The pP60gag polyprotein of the feline leukemia virus pseudotype of m1 Moloney murine sarcoma virus [m1MSV(FeLV)] was previously shown to be MSV specific and to contain murine p30 and smaller structural polypeptides. This protein was detected in m1MSV-transformed cells, and in pulse-chase studies it was found to be stable. In this study virion P60 was shown to contain murine pp12, to be phosphorylated, and to bind to nucleic acids. 32P-labeled m1MSV[FeLV) was fractionated by guanidine agarose chromatography and analyzed by gel electrophoresis. Both P60 and pp12 were found to be the major phosphoproteins, phosphorylated in both serine and threonine residues. Virion P60 bound preferentially to single-stranded DNA and RNA in a competition filter binding assay, using 125I-labeled single-stranded calf thymus DNA and various unlabeled nucleic acids. Similar phosphorylation and DNA binding properties were demonstrated for cellular P60. Thus, immunoprecipitation of cellular extracts showed that P60 was phosphorylated in both producer and nonproducer transformed cells, indicating that phosphorylation occurs independently of virus assembly. Moreover, P60 from cytoplasmic extracts was retained on single-stranded DNA-Sepharose columns, demonstrating that cellular P60 binds to DNA.

DNA↗
PubMed1975

A p60 polypeptide in the feline leukemia virus pseudotype of Moloney sarcoma virus with murine leukemia virus p30 antigenic determinants.

A 60,000-dalton polypeptide (p60) has been identified in the feline leukemia virus (FeLV) pseudotype of Moloney sarcoma virus [MSV(FeLV)]. This polypeptide is present in the purified virus complex in concentrations greater than either the murine p30 or the feline p27. Purified p60 crossreacts immunologically with murine p30 group antiserum and contains several interspecies determinants, whereas the group specific determinant of FeLV p27 is not detected. Comparison of peptide fingerprints of p60 and murine p30 show many peptides in common. Limited digestion of p60 with either trypsin or chymotrypsin produced p30-35 and p20 peptides which retain the MuLV p30 group and interspecies antigenic activities. The p30 produced by both enzymes comigrates in polyacrylamide gels with the murine p30 of MSV(FeLV), thus suggesting that p60 may be an uncleaved precursor to p30.

Chromatography, Gel↗