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Role of methylation in the induced and spontaneous expression of the avian endogenous virus ev-1: DNA structure and gene products.

Conklin, K F and Coffin, J M and Robinson, H L and Groudine, M and Eisenman, R N (1982) Role of methylation in the induced and spontaneous expression of the avian endogenous virus ev-1: DNA structure and gene products. Molecular and cellular biology, 2 (6). pp. 638-652. ISSN 0270-7306

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The endogenous avian provirus ev-1 is widespread in white leghorn chickens. Although it has no major structural defects, ev-1 has not been associated with any phenotype and is ordinarily expressed at a very low level. In this report, we describe a chicken embryo (Number 1836) cell culture containing both ev-1 and ev-6 which spontaneously expressed the ev-1 provirus. This culture released a high level of noninfectious virions containing a full complement of virion structural (gag) proteins but devoid of reverse transcriptase activity or antigen. These virions contained 70S RNA closely related to the genome of Rous-associated virus type 0, but identifiable as the ev-1 genome by oligonucleotide mapping. A fraction of the RNA molecules in the 70S complex were unusual in that they were polyadenylated 100 to 200 nucleotides downstream of the usual polyadenylation site. Eight sibling embryo cultures did not share this unusual phenotype with 1836, indicating that it was not inherited. However, an identical phenotype was inducible in the sibling cultures by treatment with 5-azacytidine, an inhibitor of DNA methylation, and the induced expression was stable for more than 10 generations. Analysis of chromatin structure and DNA methylation of the ev-1 provirus in 1836 cells revealed the presence (in a fraction of the proviruses) of both DNase I hypersensitive sites in the long terminal repeats and in gag and a pattern of cleavage sites for methyl-sensitive restriction endonuclease not found in a nonexpressing sibling. These results lend strong support to the role of DNA methylation in the control of gene expression. Additionally, they explain the lack of phenotype associated with ev-1 as due to a combination of its low expression and defectiveness in pol and env.

Item Type: Article or Abstract
Additional Information: This article is freely available in PubMed Central and at the journal's website.
PubMed ID: 14582159
PMCID: PMC369840
Grant Numbers: CA-17659, CA-20525, CA-10467, PCM 7903675, T31-GM-07310-07
Keywords or MeSH Headings: Animals; Avian leukosis virus/genetics; Chick Embryo; Chickens/virology; Chromatin/chemistry/genetics/metabolism; DNA Methylation; DNA, Viral/chemistry; Endogenous Retroviruses/genetics; Gene Expression Regulation, Viral; Genes, Viral/genetics; Genes, gag/genetics; Proviruses/genetics;
Subjects: Organisms > Viruses > RNA viruses
Molecules > Chromosomes > Chromatin
Cellular and Organismal Processes > Genetic processes > Transcription
Depositing User: Library Staff
Date Deposited: 04 Dec 2008 23:48
Last Modified: 21 May 2010 21:06

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