Chromatin structure of endogenous retroviral genes and activation by an inhibitor of DNA methylation

Abstract
The transcriptionally active ev-3 and inactive ev-1 endogenous retrovirus loci in chick cells differ in that ev-3 is undermethylated, preferentially sensitive to DNase I digestion, and contains nuclease hypersensitive sites in each of its 2 long terminal repeats. Transient exposure of cells to 5-azacytidine, a cytosine analog which cannot be methylated at the 5 position, results in the hypomethylation and transcriptional activation of ev-1, and the acquisition of at least 1 nuclease-hypersensitive site within the chromosomal domain of ev-1.