title: Construction of an Escherichia coli vector containing the major DNA adduct of activated benzo[a]pyrene at a defined site.
abstract: The mutagenic and carcinogenic substance benzo[a]pyrene reacts with DNA following activation to its corresponding 7,8-diol 9,10-epoxide (BPDE), and the major DNA adduct (BP-N2-Gua) is formed when the C(10)-position of BPDE reacts with the N2-position of guanine. It is unknown if this adduct is a premutagenic lesion in vivo. Herein, the construction and characterization of an M13mp19-based, E. coli vector that contains BP-N2-Gua located in the unique PstI restriction endonuclease recognition site at nucleotide position 6249 in the (-)-strand is described (designated, BP-N2-Gua-M13mp19). First, the oligonucleotide 5'-TGCA-3' was reacted with BPDE and a product (5'-T(BP-N2)GCA-3') was isolated by HPLC that, when enzymatically digested to deoxynucleosides, yielded an adduct that comigrated on HPLC with an authentic BP-N2-Gua deoxynucleoside standard. Second, the 5'-hydroxyl group of 5'-T-(BP-N2)GCA-3' was phosphorylated with ATP and T4 polynucleotide kinase, and the product (5'-pT(BP-N2)GCA-3') was purified by HPLC. This product is stable when heated at 80 degrees C at both neutral and alkaline pH. Third, M13mp19 was manipulated such that the sequence 5'-pTGCA-3' was selectively removed from the (-)-strand in its unique PstI recognition site, and 5'-pT(BP-N2)GCA-3' was ligated into this gap with T4 DNA ligase and ATP. The product of this reaction (BP-N2-Gua-M13mp19) was shown to be insensitive to cleavage by PstI, which suggests that a modification is located in the PstI recognition site. The most likely modification is the adduct BP-N2-Gua.
authors.affiliation: Department of Biology, Boston University, Massachusetts 02215.
authors.forename: M
authors.initials: M
authors.lastname: Benasutti
authors.forename: Z D
authors.initials: ZD
authors.lastname: Ezzedine
authors.forename: E L
authors.initials: EL
authors.lastname: Loechler
mesh_terms: D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; D001483:Base Sequence; D001564:Benzo(a)pyrene / Q000378:metabolism*; D001711:Biotransformation; D004247:DNA; D018736:DNA Adducts; D004926:Escherichia coli / Q000235:genetics*; D005822:Genetic Vectors; D016680:Genome, Bacterial; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis
chemical_list: D018736:DNA Adducts; D009838:Oligodeoxyribonucleotides; C043931:benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide-DNA; D001564:Benzo(a)pyrene; D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; D004247:DNA