Repair of O6-ethylguanine in DNA by a chromatin fraction from rat liver: transfer of the ethyl group to an acceptor protein.
Incubation of O6-[3H]ethylguanine-containing DNA with a rat liver chromatin fraction resulted in a decrease in the O6-ethylguanine content of the DNA. Analysis of the products of this reaction showed that the ethyl group had been transferred from the O6-ethylguanine to a protein acceptor. When the incubation mixture was separated on a cesium chloride gradient, the radioactivity removed from O6-ethylguanine appeared in a low-density band. This material has been isolated and subjected to trypsin digestion and high-pressure liquid chromatography analysis; it was sensitive to trypsin and the digest contained new high-pressure liquid chromatography peaks characteristic of oligopeptides. Radioactive peaks from the trypsin digestion have been digested further to the amino acid level and have been shown to contain S-[3H]ethylcysteine. Thus, we conclude that the repair activity in rat liver chromatin removes the ethyl group from O6-ethylguanine and transfers it to a cysteine moiety contained in an acceptor protein.
D000818:Animals; D002843:Chromatin / Q000378:metabolism*; D003545:Cysteine / Q000031:analogs & derivatives / Q000032:analysis; D004247:DNA / Q000096:biosynthesis*; D004260:DNA Repair; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D010446:Peptide Fragments / Q000032:analysis; D011506:Proteins / Q000378:metabolism*; D051381:Rats
D002843:Chromatin; D010446:Peptide Fragments; D011506:Proteins; C007673:6-ethylguanine; D006147:Guanine; D004247:DNA; C026826:S-ethylcysteine; D003545:Cysteine