title: A G4-DNA/B-DNA junction at codon 12 of c-Ha-ras is actively and asymmetrically methylated by DNA(cytosine-5)methyltransferase.
abstract: Oligodeoxynucleotides spanning codon 12 of the human c-Ha-ras gene were found to be exceptionally good substrates for de novo methylation by human DNA(cytosine-5)methyltransferase. In the complex formed by two complementary 30mers, only the C-rich strand was methylated by the enzyme. Guanines at the 3' end of the G-rich strand of the complex could not be completely modified by dimethyl sulfate [corrected] suggesting tetrameric bonding at these G-residues. An eight-stranded structure, composed of four duplex DNAs at one end, joined to a G4-DNA segment at the other with the junction between the two DNA forms at codon 12, can account for our results.
authors.affiliation: Division of Surgery, City of Hope, Duarte, CA 91010.
authors.forename: S S
authors.initials: SS
authors.lastname: Smith
authors.forename: D J
authors.initials: DJ
authors.lastname: Baker
authors.forename: L A
authors.initials: LA
authors.lastname: Jardines
mesh_terms: D001483:Base Sequence; D003062:Codon; D003596:Cytosine / Q000378:metabolism; D004247:DNA / Q000378:metabolism*; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000378:metabolism*; D015252:Deoxyribonucleases, Type II Site-Specific; D004121:Dimethyl Sulfoxide; D006147:Guanine; D006801:Humans; D008745:Methylation; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D016283:Proto-Oncogene Proteins p21(ras)
chemical_list: D003062:Codon; D011518:Proto-Oncogene Proteins; D006147:Guanine; D003596:Cytosine; D004247:DNA; D004248:DNA (Cytosine-5-)-Methyltransferases; D015252:Deoxyribonucleases, Type II Site-Specific; C037130:GCGC-specific type II deoxyribonucleases; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); D004121:Dimethyl Sulfoxide