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Biomedical subjects

C F Garon

Publications and source records attributed to C F Garon.

At least 91 records · Page 5Linked to original sources
PubMed1975

Arrangement of sequences in the inverted terminal repetition of adenovirus 18 DNA.

In contrast to the single-stranded circular molecules produced with denatured DNA from other adenoviruses, there was associated with nearly all circular molecules of adenovirus type 18 a visible, duplex projection. These projections had a mean contour length of 0.31 +/- 0.12 mum, equivalent to approximately 3% of genome length. Individual projections ranged in size from 0.1 to 2 mum. Alkaline sucrose gradient purification of single-stranded molecules did not affect formation of these projections, and treatment of a preparation of circular molecules with Neurospora crassa single-strand specific nucleases yielded 0.34 +/- 0.09 mum duplex fragments. Single-stranded circles did not form if a limited number of nucleotides were removed from the 3' ends of native molecules by Escherichia coli exonuclease III digestion prior to denaturation and annealing. In addition, preformed single-stranded circles could be converted to linear molecules by similar treatment. Based on the formation of specific heteroduplex structures when preparations of native DNA were denatured and reannealed and the absence of branches on linear, single-stranded molecules, we conclude that projections are generated by unusually long, inverted terminal repetitions. The repetitious sequences occur in place of rather than in addition to regular sequences. These data provide direct, visual evidence for the arrangement of bases in the inverted terminal repetition of adenovirus DNA.

Adenoviridae↗
PubMed1973

Self-complementarity of terminal sequences within plus or minus strands of adenovirus-associated virus DNA.

At least 70% of plus or minus strands of adenovirus-associated virus DNA contain self-complementary sequences at or near their termini. Self-annealing of these sequences generates circular molecules that are closed by duplex, hydrogen-bonded segments. The self-annealed segments are sensitive to exonuclease III and have a thermal stability comparable to that of double-stranded DNA molecules. Length measurements of double-stranded adenovirus-associated virus DNA molecules show a bimodal distribution, with the larger component being 10% shorter than SV40 DNA. The presence of self-complementary terminal sequences in single-stranded molecules of viral DNA has been observed previously only with DNA from adenoviruses. It is thus especially notable that adenovirus-associated virus replication is unconditionally dependent on a helper adenovirus. A possible role for terminal self-complementary sequences in viral DNA replication is suggested.

Adenoviridae↗
PubMed1972

A unique form of terminal redundancy in adenovirus DNA molecules.

A unique form of terminal redundancy has been observed in DNA molecules extracted from several human adenovirus serotypes. Electron microscopic studies reveal that single-stranded circular molecules are formed when native DNA is denatured and then annealed. Temperatures approaching the T(m) of native DNA are required to convert circles to linear molecules, indicating a high degree of self-complementarity between terminal base sequences of DNA strands. Single-stranded circles are not generated if a limited number of nucleotides (2-4%) are removed from the 3' ends of native DNA by digestion with Escherichia coli exonuclease III before denaturation and annealing. The lenght of the redundant segment appears to differ among major serotypic groups, and a possible association between increased length of the redundant segment and increased oncogenic capability of virus serotype is suggested. Evidence for the configuration of the duplex closure region of circular molecules is also presented.

Adenoviridae↗
PubMedDate not supplied

An improved method for the isolation of supercoiled DNA molecules using ion-exchange column chromatography.

An improved procedure is presented for the rapid isolation of supercoiled molecules using ion-exchange chromatography of alkali-denatured material. Under the conditions employed, contaminating cellular DNA, RNA, and nicked circular molecules are denaturable and are presented to the column as single strands while intact, covalently closed, supercoiled molecules resist denaturation and are batch eluted from the column as the only remaining duplex species. Small amounts of protein and short, duplex fragments (less than 1 kb) are removed in the void volume. There is no need for gradient fractionation. Supercoil fractions are virtually free of contamination with linear molecules as determined by electron microscopy, have an A260 nm/A280 nm ratio approaching 2.0, and are suitable for subsequent heteroduplex analysis, molecular cloning, subcloning, or restriction enzyme mapping. The method has been used successfully to purify plasmids up to 45 kb in length and to isolate rare circular replication intermediates from an overwhelming excess of contaminating linear molecules in retrovirus-infected cells.

Chromatography, Ion Exchange↗
PubMedDate not supplied

Extrachromosomal elements of spirochetes.

The spirochetes include some important pathogenic bacteria, Treponema, Borrelia and Leptospira. The pathogeneses of these spirochetes are very diverse. In an attempt to learn more about the virulence factors among the spirochetes, their genetic organization and capacity have been studied. Structural analysis of the genome in Borrelia has shown that the genome is composed of one linear maxi-chromosome with additional linear minichromosomes as well as several supercoiled circular plasmids. Moreover, the molecular analysis of the terminal ends of one of the linear minichromosomes has revealed that this unique replicon has sequence similarities with poxviruses and particularly the viral agent of African swine fever. The presence of nucleic-acid-containing vesicles and its possible role in mediating DNA transfer between borreliae is an additional, very interesting feature of these organisms. Treponema does not contain any linear DNA, chromosomal or extrachromosomal, however molecular characterization of a 2.6-kb plasmid of Treponema denticola has been performed with the aim of establishing cloning vehicles to study the virulence properties of the genus Treponema.

Borrelia↗
PubMedDate not supplied

mRNA transcripts related to full-length endogenous retroviral DNA in human cells.

Mammalian cells contain multiple copies of endogenous type C retroviral DNA sequences. Among these sequences are complete, potentially infectious proviruses, proviral DNA that is expressed only in the form of viral antigens, retroviral segments that may contribute portions of envelope (env) genes during the generation of recombinant polytropic viruses, and many subgenomic viral DNA segments that may not be expressed at all. We have previously reported the identification and molecular cloning of type C retroviral sequences from human DNA and have shown that the partial nucleotide and deduced amino acid sequences of one of the clones obtained (lambda 51) are homologous to Moloney MuLV (MoMuLV) in the gag and pol regions. The lambda 51 clone as well as several others isolated from a human DNA library contained approximately 4.3 kilobases (kb) of retroviral sequences, were deleted in the env region, and were flanked by tandem repeats unlike the long terminal repeats (LTRs) typically found in proviral DNAs (P.E.S., in preparation). We describe here the characterization of a full-length human retroviral clone (lambda 4-1) containing LTR elements as well as a putative env region. DNA-RNA hybridization experiments reveal that human cells contain species of poly(A)+ RNA that anneal to segments of the full-length retroviral DNA clone.

Cloning, Molecular↗