Biomedical subjects

M C Pascarel

Publications and source records attributed to M C Pascarel.

4 recordsLinked to original sources

PubMed1987

Spiroplasma virus 4: nucleotide sequence of the viral DNA, regulatory signals, and proposed genome organization.

The replicative form (RF) of spiroplasma virus 4 (SpV4) has been cloned in Escherichia coli, and the cloned RF has been shown to be infectious by transfection (M. C. Pascarel-Devilder, J. Renaudin, and J.-M. Bové, Virology 151:390-393, 1986). The cloned SpV4 RF was randomly subcloned and was fully sequenced by the dideoxy chain termination technique, using the M13 cloning and sequencing system. The nucleotide sequence of the SpV4 genome contains 4,421 nucleotides with a G+C content of 32 mol%. The triplet TGA is not a termination codon but, as in Mycoplasma capricolum (F. Yamao, A. Muto, Y. Kawauchi, M. Iwami, S. Iwagani, Y. Azumi, and S. Osawa, Proc. Natl. Acad. Sci. USA 82:2306-2309, 1985), probably codes for tryptophan. With these assumptions, nine open reading frames (ORFs) were identified. All nine are characterized by an ATG or GTG initiation codon, one or several termination codons, and a Shine-Dalgarno sequence upstream of the initiation codon. The nine ORFs are distributed in all three reading frames. One of the ORFs (ORF1) corresponds to the 60,000-dalton capsid protein gene. Analysis of codon usage showed that T- and A-terminated codons are preferably used, reflecting the low G+C content (32 mol%) of the SpV4 genome. The viral DNA contains two G+C-rich inverted repeat sequences. One could be involved in transcription termination and the other in initiation of cDNA strand synthesis. The SpV4 genome was found to contain at least three promoterlike sequences quasi-identical to those of eubacteria. These results fully support the bacterial origin of spiroplasmas.

Amino Acid Sequence↗

PubMed1987

Cloning and sequencing of the genome of spiroplasma virus 4.

Spiroplasma virus 4 (Sp V4) has a circular single-stranded DNA. The replicative form (RF) of Sp V4 has been purified from infected cells of Spiroplasma melliferum, strain G1, and cloned in Escherichia coli (HB101) using plasmid pBR328 as the vector. The cloned RF was shown to be infectious by transfection. The Sp V4 RF was randomly subcloned in E. coli (TG1) using the M1 3 mp8 RF as the vector and sequenced by the dideoxy chain termination technique. We found that UGA is probably not a termination codon, but codes for tryptophan. Eight open reading frames, including that for the 65,000-dalton capsid protein, have been detected; they involve all three reading frames.

Bacteriophages↗

PubMed1987

Spiroplasmas: gene structure and expression.

Upon sequencing of the SpV4 genome, eight putative open reading frames (ORFs) including that for the 65-kilodalton (kDa) capsid protein were detected. They involve all three reading frames. Three promoter sequences were found, as well as a transcription terminator and the initiation site for complementary strand synthesis. Ribosome binding sites and regulatory sequences are closely related to those of Eubacteria. Codon usage analysis showed that A and T terminated codons are preferably used. UAA is the major termination codon. Upon cloning of the full-size SpV4 replicative form, the capsid protein gene could not be expressed in Escherichia coli, whereas the spiralin gene cloned in the same bacterium is expressed. These results suggest that in spiroplasmas, as in Mycoplasma capricolum, UGA is not a termination codon, but very probably codes for tryptophan. Spiralin contains no tryptophan. Hence, its gene contains no UGA codons and can thus be expressed in E. coli. On the other hand, the gene for capsid protein has nine UGA codons and cannot be fully expressed in the bacterium. Our results fully support the bacterial origin of spiroplasmas.

Bacteria↗

PubMed1984

Characterization of spiroplasma virus group 4 (SV4).

Spiroplasma virus Group 4 was propagated, purified and characterized. The isometric capsid is made from one major protein of 60,000 Da and contains a circular single-stranded DNA molecule of 1.7 X 10(6) Da. The host-range of SV4 is limited to Subgroup I-2 spiroplasmas. The virions are released from the infected cells by a lytic process. Transfection of spiroplasmas of Subgroup I-2 by the viral DNA was demonstrated. A high efficiency of transfection was routinely obtained in the presence of polyethyleneglycol. These experiments indicate that spiroplasmas can absorb viral DNA, opening the way for cloning.

Bacteriophages↗