Spreading of DNA methylation across integrated foreign (adenovirus type 12) genomes in mammalian cells.

摘要: The establishment of de novo-generated patterns DNA methylation is characterized by the gradual spreading (I. Kuhlmann and W. Doerfler, J. Virol. 47:631-636, 1983; M. Toth, U. Lichtenberg, Proc. Natl. Acad. Sci. USA 86:3728-3732, 1989; Muller, Doerfler Mol. Biol. 214:673-683, 1990). We have used integrated adenovirus type 12 (Ad12) genomes in hamster tumor cells as a model system to study mechanism novo methylation. Ad12 induces tumors neonate hamsters, viral into genome, usually nearly intact an orientation that colinear with virion genome. weakly methylated at 5'-CCGG-3' sequences. These sequences appear be reliable indicator for state mammalian DNA. Upon explantation culture medium, gradually spreads across increasing passage numbers culture. Methylation reproducibly initiated region between 30 75 map units on genome progresses from there either direction Eventually, strongly methylated, except terminal 2 5% end, which remains hypomethylated. Similar observations been made cell lines different sites integration. In contrast, levels do not seem change after explanation several segments unique or repetitive type. Restriction (HpaII) Southern blot experiments were performed selected cloned cellular probes. data suggest foreign DNA, exist nucleotide structures chromatin arrangements can preferentially recognized responsible cells.