Miscoding by the Exocyclic and Related DNA Adducts 3,N4-Etheno-2'-deoxycytidine, 3,N4-Ethano-2'-deoxycytidine, and 3-(2-Hydroxyethyl)-2'-deoxyuridine

Abstract

3,N4-Etheno-2'-deoxycytidine, 3-(hydroxyethyl)-2'-deoxyuridine, and 3,N4-ethano-2'-deoxy-cytidine are found in DNA of cells treated with either vinyl chloride or 1,3-bis(2-chloroethyl)-nitrosourea. These exocyclic and related DNA adducts were incorporated into oligodeoxynucleotides, which were then used as templates for primer extension in reactions catalyzed by the Klenow fragment of Escherichia coli DNA polymerase I. The miscoding potential of each lesion was determined quantitatively. DNA primers were readily extended on an epsilon dC-modified template; dAMP and dTMP were incorporated opposite the lesion. With high concentrations of DNA polymerase, small amounts of fully extended reaction products containing dAMP and dGMP or one-base and two-base deletions opposite ethano-dC were formed. Primer extension was blocked partially on templates containing 3-(hydroxyethyl)-dU; dAMP and smaller amounts of dTMP and dCMP were incorporated. The frequencies of nucleotide insertion opposite each of the three lesions and the frequencies of chain extension from the 3'-primer terminus, determined by kinetic analysis, were consistent with results of experiments utilizing polyacrylamide gel electrophoresis. We conclude from these studies that epsilon dC, ethano-dC, and 3-(hydroxyethyl)-U are potentially miscoding lesions; only epsilon dC facilitates translesional synthesis.

8-(Hydroxymethyl)-3,N4-etheno-C, a Potential Carcinogenic Glycidaldehyde Product, Miscodes In Vitro Using Mammalian DNA Polymerases

“…In addition, the base pairing preferences are similar for both the 8-HM-εC and εC-containing oligonucleotides. The latter compound is closely related structurally to 8-HM-εC and it has been established that it is a mutagenic lesion (24)(25)(26)(27)(28)(29). Moreover, by molecular modeling, we showed that little difference exists in the planarity and sugar conformations of the two derivatives in duplex DNA.…”

“…The methyl carbon of the 8-HM-εC remained in the same plane with the exocyclic ring, and hydroxyl group was displaced by only 15° from the exocyclic ring plane. As proposed earlier by Zhang et al (27), the planar conformation of an adduct, such as εC, should aid the stacking interaction of this base during DNA synthesis. Similarly, the planar structure of 8-HM-εC should also contribute to the stacking interaction of this adduct during synthesis.…”

A 55-kDa protein isolated from human cells shows DNA glycosylase activity toward 3, N 4 -ethenocytosine and the G/T mismatch

“…In the case of C there is a high frequency of pairing with A or T in vitro, in both transcription (8) and replication (10,17,18). The work of Singer and Spengler (10), Zhang et al (17), and Shibutani et al (18) all agree that there is little or no C⅐C or C⅐G pairing that occurs.…”

“…These adducts became of major interest when they were found to be formed by a variety of environmental agents, as well as produced endogenously (3-7). Mutagenesis studies have shown a wide range of mutagenic frequency depending on the type of the adduct, type of mutation and the system used for detection and quantitation (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19).For more than one decade, this laboratory has focused on studies on the repair (20-26) and replication͞transcription (8-12) of etheno derivatives of dA, dC, and dG. The differing structures of the etheno adducts and their effect on base pairing and base stacking (27-31) influences both repair and replication.…”

“…These adducts became of major interest when they were found to be formed by a variety of environmental agents, as well as produced endogenously (3)(4)(5)(6)(7). Mutagenesis studies have shown a wide range of mutagenic frequency depending on the type of the adduct, type of mutation and the system used for detection and quantitation (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19).…”