Enzymatic removal of O6-methylguanine from DNA by mammalian cell extracts

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Extracts from various rat tissues were incubated with [3H]methylated DNA or chromatin in order to compare their abilities to catalyze the removal of labeled O6-methylguanine from acid precipitable DNA. Liver extracts had the greatest activity. Kidney extracts had about 35% of the activity in liver and extracts from lung, colon, small intestine and brain were much less active. The enzyme responsible for this reaction does not appear to be an N-glycosidase because no labeled O6-methylguanine could be detected in the supernatant fraction even though more than 50% of this base was lost from the DNA. The released radioactivity was present as methanol which is consistent with the possibility that the reaction may involve a demethylase action on either the DNA substrate or an oligonucleotide derived from it.

Original languageEnglish (US)
Pages (from-to)166-173
Number of pages8
JournalBiochemical and Biophysical Research Communications
Issue number1
StatePublished - Sep 14 1978

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology


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