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Biomedical subjects

G E Mark

Publications and source records attributed to G E Mark.

At least 55 records · Page 3Linked to original sources
PubMed1985

Oncogene expression in autoimmune mice.

Systemic autoimmune disease states are known to be associated with abnormal cell growth or differentiation. In the murine models of systemic lupus erythematosus (SLE), specific genotypes result in dysregulated growth of certain lymphocyte subpopulations. Although genes underlying autoimmune syndromes have been characterized by mendelian genetics, it has not yet been possible to characterize them at the molecular level. Recently, it has become clear that cellular proto-oncogenes can regulate cell growth and differentiation. Therefore, we have studied the expression of five different proto-oncogenes; myc, myb, abl, bas, and raf, in organs and cells of various autoimmune strains. These genes were selected because each has previously been associated with abnormal hemopoietic cell growth, and because each has been at least partially characterized at the molecular and functional level. We have found selective abnormal proto-oncogene expression associated with the characteristic abnormal cell growth or differentiation of lymphocytes of autoimmune mice. The lymph nodes of MRL-lpr/lpr mice are packed with unusual T cells. These had a marked increase in myb expression. There was a 20-40-fold increase in myb RNA in lymph nodes of lpr/lpr mice on several different genetic backgrounds. The gld/gld mouse has a very similar unusual T cell in the lymph nodes: it also had a comparable increase in myb RNA in the nodes. In contrast, myb expression was not elevated in the other autoimmune mouse strains lacking these abnormal T cells. Whereas such lpr/lpr mice had increased myb expression in the lymph nodes and splenic T cells, they had markedly subnormal myb expression in the thymus, an organ with high myb in normal and in the other autoimmune strains. These results suggest that one phase of intrathymic differentiation in other mice occurs in the periphery of lpr/lpr mice. The spleens of NZB and male BXSB mice had increased myc expression which was found to be associated with B cells upon cell separation. Similarly, increased bas and abl expression was associated with autoimmune B cells. The xid gene, which retards or prevents the expression of murine lupus by retarding B cell maturation, was associated in BXSB.xid, NZB.xid, and MRL-lpr/lpr.xid congenic mice with marked reduction in expression of myc, bas, and abl in the spleens containing B cells, but not of myb in the lpr/lpr.xid nodes containing primarily the unusual T cells. Raf expression was found to be associated in lpr/lpr and gld/gld mice with both the unusual T cells and splenic B cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Unusual expression of IL 2 receptors and both the c-myb and c-raf oncogenes in T cell lines and clones derived from autoimmune MRL-lpr/lpr mice.

Concomitant with their disease, autoimmune MRL-lpr/lpr mice develop a profound lymphadenopathy composed of an unusual dull Lyt-1+ population of T cells. To examine the unusual growth properties and origin of these T cells, as well as their potential role in disease, very rapidly growing T cell lines and clones have been developed from cultures of MRL-lpr/lpr spleen and LN cells. These were studied for growth receptors, oncogene expression, and surface markers. The results further demonstrate the unique nature of lpr-derived T cells and show that i) all lines and clones exhibit greatly elevated expression of both the c-myb and the c-raf oncogenes, ii) despite the reported defect in IL 2 receptor expression of mitogen-activated fresh MRL-lpr/lpr T cells, all long-term lines or clones bear large numbers of IL 2 receptors continuously and without stimulation, although iii) unlike slower growing IL 2-dependent lines from MRL-lpr/lpr mice, these rapidly growing lines and clones are poorly inhibited by anti-IL 2 receptor antibody. Such IL 2 receptor-bearing, nontransformed T cells that are easily maintained have been useful in growth factor studies.

Animals↗
PubMed1984

Primary structure of v-raf: relatedness to the src family of oncogenes.

A replication-defective, acute transforming retrovirus (murine sarcoma virus 3611) was isolated from mouse and molecularly cloned. The nucleotide sequence of 1.5 kilobases encompassing the transforming gene (v-raf) was determined. This sequence, which predicts the amino acid sequence of a gag-raf fusion protein, terminates 180 nucleotides from the 3' end of the acquired cellular sequence. Comparison of the predicted amino acid sequence of v-raf with the predicted amino acid sequences of other oncogenes reveals significant homologies to the src family of oncogenes. There is a lack of homology within the sequence of the tyrosine acceptor domain described for the phosphotyrosine kinase members of the src family of transforming proteins. Phylogenetic arrangement of this family of oncogenes suggests that tyrosine-specific phosphorylation may be a recently acquired activity.

Amino Acid Sequence↗
PubMed1984

A common onc gene sequence transduced by avian carcinoma virus MH2 and by murine sarcoma virus 3611.

A common cellular sequence was independently transduced by avian carcinoma virus MH2 (v-mht) and murine sarcoma virus (MSV) 3611 (v-raf). Comparison of the nucleotide sequences of v-mht and v-raf revealed a region of homology that extends over 969 nucleotides. The homology between the corresponding amino acids was about 95 percent with only 19 of 323 amino acids being different. With this example, 5 of the 19 known different viral onc genes have been observed in viruses of different taxonomic groups. These data indicate that (i) the number of cellular proto-onc genes is limited because, like other viruses of different taxonomic groups, MH2 and MSV 3611 have transduced the same onc gene-specific sequences from different cell species and (ii) that specific deletion and linkage of the same proto-onc sequences to different viral vector elements affect the oncogenic potential of the resulting viruses. The difference in transformation capabilities of MH2 and MSV 3611 serves as an example.

Alpharetrovirus↗
PubMed1984

Nucleotide sequence of avian carcinoma virus MH2: two potential onc genes, one related to avian virus MC29 and the other related to murine sarcoma virus 3611.

The 5.2-kilobase (kb) RNA genome of avian carcinoma virus MH2 has the genetic structure 5'-delta gag (0.2 kb)- mht (1.2 kb)-myc (1.4 kb)-c (0.4 kb)-poly(A) (0.2 kb)-3'. delta gag is a partial retroviral core protein gene, mht and myc are cell-derived MH2-specific sequences, and c is the 3'-terminal retroviral vector sequence. Here we have determined the nucleotide sequence of 3.5 kb from the 3' end of delta gag to the 3' end of molecularly cloned proviral MH2 DNA, in order to elucidate the genetic structure of the virus and to compare it with other mht - and myc-containing oncogenic viruses as well as with the chicken proto-myc gene. The following results were obtained: (i) delta gag- mht forms a hybrid gene with a contiguous reading frame of 2682 nucleotides that terminates with a stop codon near the 3' end of mht . The 3' 969 nucleotides of mht up to the stop codon are 80% sequence related to the onc-specific raf sequence of murine sarcoma virus 3611 (94% homologous at the deduced amino acid level). (ii) The myc sequence is preceded by an RNA splice acceptor site shared with the cellular proto-myc gene, beyond which it is colinear up to a 3'-termination codon and 40 noncoding nucleotides with the myc sequences of avian retrovirus MC29 and chicken proto-myc. Thus, myc forms, together with a 5' retroviral exon, a second MH2-specific gene. (iii) myc is followed by the 3'-terminal c region of about 400 nucleotides, which is colinear with that of Rous sarcoma virus except for a substitution near the 5' end of the long terminal repeat. It is concluded that MH2 contains two genes with oncogenic potential, the delta gag- mht gene, which is closely related to the delta gag-raf transforming gene of MSV 3611, and the myc gene, which is related to the transforming gene of MC29. Furthermore, it may be concluded that the cellular proto-onc genes, which on sequence transduction become viral onc genes, are a small group because among the 19 known onc sequences, 5 are shared by different taxonomic groups of viruses of which the mht /raf homology is the closest determined so far.

Amino Acid Sequence↗
PubMed1984

Envelope gene sequence of two in vitro-generated mink cell focus-forming murine leukemia viruses which contain the entire gp70 sequence of the endogenous nonecotropic parent.

The mink cell focus-forming (MCF) class of recombinant murine leukemia viruses (CI-1 to 4) were isolated from iododeoxyuridine-induced C3H/MCA 5 cells in culture and molecularly cloned. These genomes included infectious (CI-3) and defective (CI-4) recombinants. A total of 2,408 nucleotides of CI-3 virus DNA, including the MCF envelope gene, were sequenced and compared with ecotropic, dual-tropic, and xenotropic sequences. The extent of recombinational exchange in CI-3 was from 145 nucleotides 3' of the splice acceptor site for the envelope mRNA to nucleotide 1,722, between the end of gp70 and the beginning of Prp15E. Thus, the entire gp70 sequence of the endogenous nonecotropic parent was present in this recombinant. The nature and location of the recombinant junctions were consistent with a mechanism involving DNA exchange during reverse transcription. Comparison of the substituted sequence in CI-3 with that of Moloney MCF virus suggests a very close relationship, if not identity, between the endogenous dual-tropic proviruses from which they were derived. A nonidentity of xenotropic and MCF gp70s was observed, suggesting that xenotropic murine leukemia viruses are not the nonecotropic parent of the env gene of MCF murine leukemia viruses. The replication-defective virus CI-4 had a 684-nucleotide deletion present in the env gene, eliminating the hydrophobic regions within the gp70 carboxy end and the p15E amino end. This sequence was bordered by an 11-nucleotide direct repeat in CI-3 viral DNA.

Amino Acid Sequence↗
PubMed1983

Cellular toxicity of urinary catheters.

The cellular compatibility of each of several brands of urinary catheters available on the Australian market was measured by means of cell-culture methods, a rabbit intramuscular implant test, and the traditional mouse systemic toxicity test. Good agreement was obtained between the in-vitro tests and the rabbit implant tests (although the cell-culture tests were simpler, more rapid, more sensitive, and quantitative). The mouse systemic toxicity test was insensitive, and detected no toxic samples. The cell-culture and rabbit-implant test results indicated that some urinary catheters can release substances harmful to mammalian cells. Such substances may contribute to the clinical reactions of urethritis and strictures after urethral catheterization.

Animals↗
PubMed1983

Structure and biological activity of v-raf, a unique oncogene transduced by a retrovirus.

We have molecularly cloned a unique acutely transforming replication-defective mouse type C virus (3611-MSV) and characterized its acquired oncogene. The viral genome closely resembles Moloney (M) murine leukemia virus (MuLV), except for a substitution in M-MuLV in the middle of p30 and the middle of the polymerase gene (pol). Heteroduplex analysis revealed that 2.4 kilobases of M-MuLV DNA were replaced by 1.2 kilobases of cellular DNA. The junctions between viral and cellular sequences were determined by DNA sequence analysis to be 517 nucleotides into the p30 sequence and 1,920 nucleotides into the polymerase sequence. Comparison of the transforming gene from 3611-MSV, designated v-raf, with previously isolated retrovirus oncogenes either by direct hybridization or by comparison of restriction fragments of their cellular homologs shows it to be unique. Transfection of NIH 3T3 cells with cloned 3611-MSV proviral DNA leads to highly efficient transformation and the recovered virus elicits tumors in mice typical of the 3611-MSV virus. Transfected NIH 3T3 cells express two 3611-MSV-specific polyproteins (P75 and P90), both of which contain NH2-terminal gag gene-encoded components linked to the acquired sequence (v-raf) translational product. The cellular homolog, c-raf, is present in one or two copies per haploid genome in mouse and human DNA.

Animals↗
PubMed1982

Molecular cloning of a family of retroviral sequences found in chimpanzee but not human DNA.

A number of retrovirus-like sequences have been cloned from chimpanzee DNA which constitute the chimpanzee homologs of the endogenous colobus type C virus CPC-1. One of the clones contains a nearly complete viral genome, but others have sustained deletions of 1 to 2 kilobases in the polymerase gene. The pattern of related sequences detected in other primate species is consistent with the genetic transmission of these sequences for millions of years. However, the appropriately related sequences have not been detected in human, gibbon, or orangutan DNAs. These results suggest either that this family of sequences has been deleted from humans, gibbons, and orangutans, or that the genes were recently acquired in the chimpanzee and gorilla lineages.

Animals↗
PubMed1979

Nuclear accumulation of influenza viral RNA transcripts and the effects of cycloheximide, actinomycin D, and alpha-amanitin.

The use of virus-specific (32)P-labeled complementary DNA and (125)I-labeled virion RNA as hybridization probes has allowed us to quantitate the number of molecules of complementary RNA (cRNA) and progeny virion RNA in MDCK cells infected with influenza virus. We compared the distribution of cRNA between the nucleus and the cytoplasm in cycloheximide-treated cells to that found in untreated cells, beginning 1 h after infection. A greater percentage of the total cRNA was detected in the nucleus of the drug-treated cells at all times investigated. For the first 2 h after infection about 50% of the cRNA synthesized in the cycloheximide-treated cells was found in the nucleus. These nuclear cRNA molecules were characterized and shown to be polyadenylated transcripts of each of the genome virion RNA segments. Viral cRNA synthesis was not completely inhibited by the addition of actinomycin D at the beginning of infection, with or without the concomitant addition of cycloheximide. A large fraction (about 90%) of these cRNA sequences were detected in the nucleus. Characterization of these nuclear cRNA molecules showed that they contained polyadenylic acid and represented transcripts of both those segments coding for proteins synthesized predominantly early after infection ("early" proteins) and those virion RNA segments coding for "late" proteins. Also, in vitro translation of these cRNA molecules showed that they were functional virus mRNA's. In contrast to actinomycin D, alpha-amanitin completely inhibited cRNA synthesis when added at the beginning of infection, and addition of this drug after 1.5 h had no effect on further cRNA synthesis.

Amanitins↗
PubMed1979

Avian sarcoma virus-transformed quail clones defective in the production of focus-forming virus.

Quail embryo fibroblasts were infected at low multiplicity with avian sarcoma virus, and transformed cells were selected by their ability to form colonies in agar. Five clones that failed to produce focus-forming virus were examined for (i) intactness of the integrated proviral DNA, (ii) intracellular viral RNA production, (iii) intracellular viral antigen production, (iv) production of virus particles, and (v) rescue of a functional src gene and of parental host range determinants by superinfection with Rous-associated virus-60, an avian leukosis virus of subgroup E. Deletions in the integrated viral DNA were apparent in three of the five nonproducer clones. In one clone producing focus-forming virus, analysis of the integrated viral DNA revealed an insertion in the region of the genome that codes for src.

Animals↗
PubMed1978

Analysis of unintegrated avian RNA tumor virus double-stranded DNA intermediates.

Previous studies by Guntaka et al. have shown that the unintegrated DNA intermediates of avian RNA tumor virus replication can be readily isolated from cultures of the quail tumor line QT-6 at 1 day after infection. The intermediates include double-stranded linear and covalently closed circular DNA species. Using the analysis procedure of Southern together with previously obtained information regarding the sites of action of certain restriction endonucleases on avian sarcoma virus DNA, we have further characterized the viral DNA intermediates. Evidence is presented that, relative to the RNA genome, most of the linear species possess a direct terminal sequence redundancy equivalent to 0.5 X 10(6) +/- 0.3 X 10(6) daltons of double-stranded DNA. Some of the circular forms also possess a sequence redundancy of 0.21 X 10(6) +/- 0.03 X 10(6) daltons.

Alpharetrovirus↗