Synthesis and characterization of covalent adducts derived from the binding of benzo[a]pyrene diol expoxide to a -GGG- sequence in a deoxyoligonucleotide.
Direct synthesis and purification procedures are described for the preparation of adducts derived from the covalent binding of 7R,8S-dihydroxy-9S,10R-epoxy-7,8,9,10-tetrahydro-benzo[a]pyrene [(+)-anti-BPDE or (+)-BPDE 2] to each of the three guanine residues (trans-N2-dG lesions) in the oligodeoxyribonucleotide d(CTATG1G2G3TATC). The positions of the modified Gs are defined by Maxam-Gilbert sequencing techniques. Six different oligonucleotides with one or two precisely positioned (+)-anti-BPDE residues are identified. The absorbance, circular dichroism and fluorescence characteristics are changed upon formation of duplexes with the complementary strands d(GATACCCATAG). In the doubly-modified oligonucleotides, a broad, excimer-like long wavelength fluorescence emission band is observed with a maximum near 455 nm only if the two (+)-anti-BPDE-modified Gs are adjacent to one another. The covalently attached (+)-anti-BPDE residues decrease the thermodynamic stabilities of the duplexes; their melting points are markedly dependent on the position of the lesions, being highest with the (+)-anti-BPDE residue at G1 (Tm = 40 degrees C, only 2 degrees C lower than in the case of the unmodified oligonucleotide) and lowest when it is situated at G3 (Tm = 29 degrees C). The implications of these and other physical characteristics are discussed. The facile synthesis of these or similar site-specific and stereochemically defined (+)-trans-anti-BPDE-N2-dG lesions in runs of contiguous guanines in oligodeoxyribonucleotides of specified base sequence should be useful for the design of site-directed mutagenesis studies in vitro and in vivo.
Mao
B
B
Chemistry Department, New York University, NY 10003.
Xu
J
J
Li
B
B
Margulis
L A
LA
Smirnov
S
S
Ya
N Q
NQ
Courtney
S H
SH
Geacintov
N E
NE
D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000302:isolation & purification* / Q000378:metabolism*; D018736:DNA Adducts / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D004586:Electrophoresis; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000302:isolation & purification* / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
D018736:DNA Adducts; D009841:Oligonucleotides; C043931:benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide-DNA; D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; D004247:DNA