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C Upton

Publications and source records attributed to C Upton.

83 records · Page 5Linked to original sources
PubMed1986

Tumorigenic poxviruses: analysis of viral DNA sequences implicated in the tumorigenicity of Shope fibroma virus and malignant rabbit virus.

The DNA sequence has been determined for a 7-kb region within the terminal inverted repeats (TIR) of Shope fibroma virus (SFV), a poxvirus which induces benign fibromas in rabbits. This region of the SFV TIR, which flanks the junction of the TIR with the unique internal sequences of the viral genome, had previously been shown to be also present in the genome of malignant rabbit virus (MRV), a hybrid poxvirus derived from a recombination event between SFV and a related leporipoxvirus, myxoma. Unlike SFV, the recombinant MRV induces an invasive profile of tumors in infected rabbits, but the capacity to induce proliferant fibromas appears to have been derived from SFV. These SFV DNA sequences have been analyzed and their genetic organization shows a unique tandem arrangement of three large open reading frames (ORFs) which share considerable homology with each other. Very short spacer sequences are present between the majority of ORFs, all of which are transcribed toward the terminal hairpins of SFV. Unusual dyad symmetries flank two of the most closely related ORFs and evidence is presented that one SFV ORF (T9-L) which maps precisely at the TIR/unique sequence boundary was truncated during transposition to the left terminus from a progenitor copy (T9-R) at the right terminus. The origin of these putative viral genes is considered in light of the recent observation (C. Upton and G. McFadden, 1986, Mol. Cell. Biol. 6, 265-276) that a subset of this region of the SFV genome is closely related to, and may have been originally derived from, an endogenous covalently closed circular plasmid species detected in uninfected rabbit cells.

Amino Acid Sequence↗
PubMed1986

Replication and resolution of cloned poxvirus telomeres in vivo generates linear minichromosomes with intact viral hairpin termini.

The covalently closed terminal hairpins of the linear duplex-DNA genomes of the orthopoxvirus vaccinia and the leporipoxvirus Shope fibroma virus (SFV) have been cloned as imperfect palindromes within circular plasmids in yeast cells and recombination-deficient Escherichia coli. The viral telomeres inserted within these recombinant plasmids are equivalent to the inverted-repeat structures detected as telomeric replicative intermediates during poxvirus replication in vivo. Although the telomeres of vaccinia and SFV show little sequence homology, the termini from both viral genomes exist as AT-rich terminal hairpins with extrahelical bases and alternate "flip-flop" configurations. Using an in vivo replication assay in which circular plasmid DNA was transfected into poxvirus-infected cells, we demonstrated the efficient replication and resolution of the cloned imperfect palindromes to bona fide hairpin termini. The resulting linear minichromosomes, which were readily purified from transfected cells, were shown by restriction enzyme mapping and by electron microscopy to have intact covalently closed hairpin termini at both ends. In addition, staggered unidirectional deletion derivatives of both the cloned vaccinia and SFV telomeric palindromes localized an approximately 200-base-pair DNA region in which the sequence organization was highly conserved and which was necessary for the resolution event. These data suggest a conserved mechanism of the resolution of poxvirus telomeres.

Base Sequence↗
PubMed1986

Identification and nucleotide sequence of the thymidine kinase gene of Shope fibroma virus.

The thymidine kinase (TK) gene of Shope fibroma virus (SFV), a tumorigenic leporipoxvirus, was localized within the viral genome with degenerate oligonucleotide probes. These probes were constructed to two regions of high sequence conservation between the vaccinia virus TK gene and those of several known eucaryotic cellular TK genes, including human, mouse, hamster, and chicken TK genes. The oligonucleotide probes initially localized the SFV TK gene 50 kilobases (kb) from the right terminus of the 160-kb SFV genome within the 9.5-kb BamHI-HindIII fragment E. Fine-mapping analysis indicated that the TK gene was within a 1.2-kb AvaI-HaeIII fragment, and DNA sequencing of this region revealed an open reading frame capable of encoding a polypeptide of 176 amino acids possessing considerable homology to the TK genes of the vaccinia, variola, and monkeypox orthopoxviruses and also to a variety of cellular TK genes. Homology matrix analysis and homology scores suggest that the SFV TK gene has diverged significantly from its counterpart members in the orthopoxvirus genus. Nevertheless, the presence of conserved upstream open reading frames on the 5' side of all of the poxvirus TK genes indicates a similarity of functional organization between the orthopoxviruses and leporipoxviruses. These data suggest a common ancestral origin for at least some of the unique internal regions of the leporipoxviruses and orthopoxviruses as exemplified by SFV and vaccinia virus, respectively.

Base Sequence↗
PubMed1986

DNA sequence homology between the terminal inverted repeats of Shope fibroma virus and an endogenous cellular plasmid species.

DNA hybridization experiments indicate that the genome of a tumorigenic poxvirus. Shope fibroma virus (SFV), possesses sequence homology with DNA isolated from uninfected rabbit cells. Southern blotting experiments, either with high-complexity rabbit DNA as probe and SFV restriction fragments as targets or with high-specific activity, 32P-labeled, cloned SFV sequences as probes and rabbit DNA as target, indicate that the homologous sequences map at two locations within the viral genome, one in each copy of the terminal inverted repeat sequences. Unexpectedly, Southern blots revealed that the homologous host sequences reside in a rabbit extrachromosomal DNA element. This autonomous low-molecular-weight DNA species could be specifically amplified by cycloheximide treatment and was shown by isopycnic centrifugation in cesium chloride-ethidium bromide to consist predominantly of covalently closed circular DNA molecules. DNA sequencing of pSIC-9, a cloned 1.9-kilobase fragment of the rabbit plasmid species, indicated extensive homology at the nucleotide level over a 1.5-kilobase stretch of the viral terminal inverted repeat. Analysis of open reading frames in both the plasmid and SFV DNA revealed that (i) the N-terminal 157-amino acid sequence of a potential 514-amino acid SFV polypeptide is identical to the N-terminal 157 amino acids of one pSIC-9 open reading frame, and (ii) a second long pSIC-9 open reading frame of 361 amino acids, although significantly diverged from the comparable nucleotide sequence in the virus, possessed considerable homology to a family of cellular protease inhibitors, including alpha 1-antichymotrypsin, alpha 1-antitrypsin, and antithrombin III. The potential role of such cellular plasmid-like DNA species as a mediator in the exchange of genetic information between the host cell and a cytoplasmically replicating poxvirus is discussed.

Amino Acid Sequence↗
PubMed1985

Tumorigenic poxviruses: genomic organization of malignant rabbit virus, a recombinant between Shope fibroma virus and myxoma virus.

The genome of malignant rabbit virus (MRV), a newly discovered tumorigenic poxvirus of rabbits, has been analyzed using cloned DNA probes from Shope fibroma virus (SFV) and myxoma virus. Under high stringency conditions for Southern blotting such that SFV probes do not cross-hybridize with myxoma virus DNA, it is demonstrated that greater than 90% of the MRV genome has been derived from myxoma virus, and that approximately 10 kb of SFV-derived sequences have substituted for a similar amount of myxoma sequences. Mapping of the MRV genome indicates that the SFV sequences are present in two regions of the genome, one in each copy of the MRV terminal inverted repeat sequence. Furthermore, fine mapping studies of the integration sites for SFV into the myxoma background show that these SFV sequences are not symmetrical with respect to the left and right genomic termini. At the left end, 4 kb of SFV-derived DNA maps between 6 and 10 kb from the terminus, while at the right end about 5.5 kb of SFV sequences are found to extend at least 1 kb further toward the unique internal sequences. Based on this asymmetrical bipartite distribution of SFV sequences in MRV, a two-stage model to rationalize the origin of MRV is proposed. This model postulates an initial recombination event similar to gene conversion between myxoma and SFV at the right terminus of myxoma, followed by an incomplete transposition of only part of these SFV sequences to the left terminus.

Animals↗
PubMed1985

Plasma concentrations after oral or intramuscular vitamin K1 in neonates.

One hundred and seven healthy, breast fed infants received 1 mg vitamin K1 either at birth (orally or intramuscularly) or with the first feed (orally). Venous blood samples collected in the next 24 hours were assayed for plasma vitamin K1. In babies given the vitamin orally at birth, the peak median concentration (73 ng/ml) occurred at four hours. By 24 hours median plasma concentrations had fallen to 23 ng/ml and 35 ng/ml in the groups fed vitamin K1 at birth or with the first feed, respectively; this difference was not, however, significant. Plasma concentrations after intramuscular injection exceeded those in the oral groups at all comparable times, with a peak median concentration of 1781 ng/ml at 12 hours falling to 444 ng/ml at 24 hours. Since median plasma vitamin K1 concentrations 24 hours after oral administration were some 100 times and 1000 times greater than previously estimated adult and newborn values respectively, this study supports giving vitamin K1 orally at birth to well, mature babies to protect against early haemorrhagic disease of the newborn. Further studies are needed to determine the optimum dose for protection over subsequent weeks.

Administration, Oral↗
PubMed1983

Expression of eight unrelated Muc+ plasmids in eleven DNA repair-deficient E. coli strains.

23 plasmids from different incompatibility groups were tested for their ability to increase post-UV survival and UV-induced reversion to Arg+ in Escherichia coli strain AB1157 argE3 8 plasmids increased mutagenesis, of which 7 increased UV resistance. The exception, plasmid R391, sensitized AB1157 to UV. All 8 plasmids were absolutely dependent upon host recA+ and lexA+ genotypes for expression of these functions, but were independent of uvrA+, uvrB+, umuC+, recF+, polA+, uvrD+ or recL+. E. coli KMBL91 uvrE was sensitized to UV by R391, but protected by only 3 plasmids. All 8 plasmids restored mutation frequency in the non-mutable TK501 uvrB umuC strain to levels found in the JC3890 uvrB umuC+ parent strain. R391 sensitized TK501 to UV, but all other plasmids increased survival in the strain by over 1000-fold to levels found in the JC3890 uvrB umuC+ R+ strains. Plasmid R391 reduced the UV-protecting effect of R46 when both were present in strain TK501. Mutation frequencies were higher in TK501 (R46) than in TK501 (R391); in TK501 (R46/R391) they were slightly lower than in TK501 (R46).

Bacterial Proteins↗
PubMed1982

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Clinical Trials as Topic↗
PubMed1981

Absence of ultraviolet-inducible DNA polymerase I-like activity in Escherichia coli strains harbouring R plasmids.

No DNA polymerase I-like activity was found associated with the ultraviolet (u.v.)-protecting plasmids R205, R46 or pKM101 in either uninduced or u.v.-induced wild-type or DNA polymerase I-deficient strains of Escherichia coli. Nor was any plasmid-associated polymerase activity detectable in similar systems containing u.v.-irradiated DNA as template. However, plasmids R205, R46 and pKM101 still increased survival and mutagenesis of the polymerase I-deficient E. coli strain after u.v. irradiation.

DNA Polymerase I↗