DNA DEMETHYLATION IN-VITRO - INVOLVEMENT OF RNA

An in vitro system for studying DNA demethylation has been established using extracts from tissue culture cells, this reaction, which is unu sually resistant to proteinase K, takes place through the removal of a 5-methylcytosine nucleotide unit from the DNA substrate end its conve rsion to an RNase-sensitive form. It is likely that this represents th e in vivo mechanism, as well, Since extracts from L8 mybolasts specifi cally demethylate an alpha-actin gene, while extracts from F9 teratoca rcinoma cells specifically demodify the Aprt CpG island. After pretrea tment with proteinase K, these extracts demethylate both genes equally , suggesting that gene specificity may be controlled by protein factor s.