METHYLATION OF ADENOVIRUS GENES IN TRANSFORMED-CELLS AND INVITRO - INFLUENCE ON THE REGULATION OF GENE-EXPRESSION

  • 1 January 1981
    • journal article
    • research article
    • Vol. 25  (1) , 13-15
Abstract
An inverse correlation was described between the levels of DNA methylation in specific segments of adenovirus DNA integrated into the genomes of transformed and tumor cells and the extent to which these segments are expressed as mRNA. In the adenovirus type 2 (Ad2)-transformed hamster cell lines HE2 and HE3, the virus-specific DNA binding protein (DBP) is not expressed, and the DNA in the DBP gene is completely methylated in all 5''-CCGG-3'' sites. At least part of the late promoter/leader sequence of the DBP gene is present in cell lines HE2 and HE3. In line HE1, the DBP is expressed, and the DNA in the DBP gene is unmethylated at the 5''-CCGG-3'' (HpaII) sites. The late promoter/leader sequence of the DBP gene is expressed in cytoplasmic RNA isolated from line HE1. The effect of DNA methylation was tested in vitro in a microinjection system using Xenopus laevis oocytes. Unmethylated DNA fragments of Ad2 (E2a region) were found to serve as active templates. When the same fragments are methylated at the 5''-CCGG-3'' sites by the HpaII DNA-methyltransferase, viral RNA synthesis is inhibited upon microinjection into oocyte nuclei. DNA methylated at highly specific sites is somehow involved in the regulation of gene expression.