Base selectivity and effects of sequence and DNA secondary structure on the formation of covalent adducts derived from the equine estrogen metabolite 4-hydroxyequilenin

Alexander Kolbanovskiy, Vladimir Kuzmin, Anant Shastry, Marina Kolbanovskaya, Dandan Chen, Minsun Chang, Judith L. Bolton, Nicholas Geacintov

Research output: Contribution to journalArticle

Abstract

Equilenin, an important component of a widely prescribed hormone replacement formualtion for postmenopausal women, is metabolized by mammalian P450 enzymes to the catechol 4-hydroxyequilenin (4-OHEN). The oxidized o-quinone derivative of 4-OHEN is known to form cyclic covalent adducts with DNA [Bolton, J. (1998) Chem. Res. Toxicol. 11, 1113] in vitro and in vivo. The characteristics of 4-OHEN-DNA adduct formation were investigated with the oligonucleotides 5′-d(CCATCGCTACC) (I), its complementary strand 5′-d(GGTAGCGATGG) (II), one rich in C and the other in G, and the duplexes I·II. The identities of the modified bases were elucidated in terms of four stereoisomeric 4-OHEN-2′-deoxynucleoside standards described earlier [Shen et al. (2001) Chem. Res. Toxicol. 11, 94; Embrechts et al. J. Mass Spectrom. 36, 317]. The reactions of 4-OHEN with C are favored overwhelmingly in both single-stranded I and II with no guanine adducts observed in either case, and only minor proportions of A adducts were detected in sequence II. However, guanine adducts are observed in oligonucleotides that contain only G and unreactive T residues. The relative levels of cyclic covalent adducts observed in single-stranded I, II, and duplex I·II are ∼54:21:5, with only the end C groups in I modified in the I·II duplex. When 4-OHEN is reacted with calf thymus DNA, the reaction yield of cyclic adducts is more than ∼103-fold lower than in I. The cyclic 4-OHEN adducts lead to a pronounced thermal destabilization of duplexes I·II. Overall, cyclic adduct formation is markedly dependent on the sequence context and secondary structure of the DNA. The latter effect is attributed to the poor accessibilities of 4-OHEN to the reactive nucleotide Watson-Crick hydrogen-bonding interface in the interior of the duplex. In the single-stranded oligonucleotides I and II, the strikingly different selectivities of adduct formation are attributed to the formation of noncovalent preassociation complexes that favor reaction geometries with C, rather than with A or G. Finally, the levels of several typical biomarkers of oxidative DNA damage (including 8-oxo-2′-deoxyguanosine) are formed in I in aqueous solutions with a yield at least 10 times smaller than the yield of cyclic 4-OHEN-dC adducts under identical reaction conditions.

Original languageEnglish (US)
Pages (from-to)1737-1747
Number of pages11
JournalChemical Research in Toxicology
Volume18
Issue number11
DOIs
StatePublished - Nov 2005

Fingerprint

Metabolites
Oligonucleotides
Horses
Estrogens
DNA Adducts
Guanine
Equilenin
DNA
Biomarkers
Hydrogen Bonding
Cytochrome P-450 Enzyme System
DNA Damage
Hydrogen bonds
Nucleotides
Hot Temperature
Hormones
Derivatives
Geometry
4-hydroxy-equilenin

ASJC Scopus subject areas

  • Drug Discovery
  • Organic Chemistry
  • Chemistry(all)
  • Toxicology
  • Health, Toxicology and Mutagenesis

Cite this

Base selectivity and effects of sequence and DNA secondary structure on the formation of covalent adducts derived from the equine estrogen metabolite 4-hydroxyequilenin. / Kolbanovskiy, Alexander; Kuzmin, Vladimir; Shastry, Anant; Kolbanovskaya, Marina; Chen, Dandan; Chang, Minsun; Bolton, Judith L.; Geacintov, Nicholas.

In: Chemical Research in Toxicology, Vol. 18, No. 11, 11.2005, p. 1737-1747.

Research output: Contribution to journalArticle

Kolbanovskiy, Alexander ; Kuzmin, Vladimir ; Shastry, Anant ; Kolbanovskaya, Marina ; Chen, Dandan ; Chang, Minsun ; Bolton, Judith L. ; Geacintov, Nicholas. / Base selectivity and effects of sequence and DNA secondary structure on the formation of covalent adducts derived from the equine estrogen metabolite 4-hydroxyequilenin. In: Chemical Research in Toxicology. 2005 ; Vol. 18, No. 11. pp. 1737-1747.
@article{61731f61cac1477c8cb145a6bbc0c5a6,
title = "Base selectivity and effects of sequence and DNA secondary structure on the formation of covalent adducts derived from the equine estrogen metabolite 4-hydroxyequilenin",
abstract = "Equilenin, an important component of a widely prescribed hormone replacement formualtion for postmenopausal women, is metabolized by mammalian P450 enzymes to the catechol 4-hydroxyequilenin (4-OHEN). The oxidized o-quinone derivative of 4-OHEN is known to form cyclic covalent adducts with DNA [Bolton, J. (1998) Chem. Res. Toxicol. 11, 1113] in vitro and in vivo. The characteristics of 4-OHEN-DNA adduct formation were investigated with the oligonucleotides 5′-d(CCATCGCTACC) (I), its complementary strand 5′-d(GGTAGCGATGG) (II), one rich in C and the other in G, and the duplexes I·II. The identities of the modified bases were elucidated in terms of four stereoisomeric 4-OHEN-2′-deoxynucleoside standards described earlier [Shen et al. (2001) Chem. Res. Toxicol. 11, 94; Embrechts et al. J. Mass Spectrom. 36, 317]. The reactions of 4-OHEN with C are favored overwhelmingly in both single-stranded I and II with no guanine adducts observed in either case, and only minor proportions of A adducts were detected in sequence II. However, guanine adducts are observed in oligonucleotides that contain only G and unreactive T residues. The relative levels of cyclic covalent adducts observed in single-stranded I, II, and duplex I·II are ∼54:21:5, with only the end C groups in I modified in the I·II duplex. When 4-OHEN is reacted with calf thymus DNA, the reaction yield of cyclic adducts is more than ∼103-fold lower than in I. The cyclic 4-OHEN adducts lead to a pronounced thermal destabilization of duplexes I·II. Overall, cyclic adduct formation is markedly dependent on the sequence context and secondary structure of the DNA. The latter effect is attributed to the poor accessibilities of 4-OHEN to the reactive nucleotide Watson-Crick hydrogen-bonding interface in the interior of the duplex. In the single-stranded oligonucleotides I and II, the strikingly different selectivities of adduct formation are attributed to the formation of noncovalent preassociation complexes that favor reaction geometries with C, rather than with A or G. Finally, the levels of several typical biomarkers of oxidative DNA damage (including 8-oxo-2′-deoxyguanosine) are formed in I in aqueous solutions with a yield at least 10 times smaller than the yield of cyclic 4-OHEN-dC adducts under identical reaction conditions.",
author = "Alexander Kolbanovskiy and Vladimir Kuzmin and Anant Shastry and Marina Kolbanovskaya and Dandan Chen and Minsun Chang and Bolton, {Judith L.} and Nicholas Geacintov",
year = "2005",
month = "11",
doi = "10.1021/tx050190x",
language = "English (US)",
volume = "18",
pages = "1737--1747",
journal = "Chemical Research in Toxicology",
issn = "0893-228X",
publisher = "American Chemical Society",
number = "11",

}

TY - JOUR

T1 - Base selectivity and effects of sequence and DNA secondary structure on the formation of covalent adducts derived from the equine estrogen metabolite 4-hydroxyequilenin

AU - Kolbanovskiy, Alexander

AU - Kuzmin, Vladimir

AU - Shastry, Anant

AU - Kolbanovskaya, Marina

AU - Chen, Dandan

AU - Chang, Minsun

AU - Bolton, Judith L.

AU - Geacintov, Nicholas

PY - 2005/11

Y1 - 2005/11

N2 - Equilenin, an important component of a widely prescribed hormone replacement formualtion for postmenopausal women, is metabolized by mammalian P450 enzymes to the catechol 4-hydroxyequilenin (4-OHEN). The oxidized o-quinone derivative of 4-OHEN is known to form cyclic covalent adducts with DNA [Bolton, J. (1998) Chem. Res. Toxicol. 11, 1113] in vitro and in vivo. The characteristics of 4-OHEN-DNA adduct formation were investigated with the oligonucleotides 5′-d(CCATCGCTACC) (I), its complementary strand 5′-d(GGTAGCGATGG) (II), one rich in C and the other in G, and the duplexes I·II. The identities of the modified bases were elucidated in terms of four stereoisomeric 4-OHEN-2′-deoxynucleoside standards described earlier [Shen et al. (2001) Chem. Res. Toxicol. 11, 94; Embrechts et al. J. Mass Spectrom. 36, 317]. The reactions of 4-OHEN with C are favored overwhelmingly in both single-stranded I and II with no guanine adducts observed in either case, and only minor proportions of A adducts were detected in sequence II. However, guanine adducts are observed in oligonucleotides that contain only G and unreactive T residues. The relative levels of cyclic covalent adducts observed in single-stranded I, II, and duplex I·II are ∼54:21:5, with only the end C groups in I modified in the I·II duplex. When 4-OHEN is reacted with calf thymus DNA, the reaction yield of cyclic adducts is more than ∼103-fold lower than in I. The cyclic 4-OHEN adducts lead to a pronounced thermal destabilization of duplexes I·II. Overall, cyclic adduct formation is markedly dependent on the sequence context and secondary structure of the DNA. The latter effect is attributed to the poor accessibilities of 4-OHEN to the reactive nucleotide Watson-Crick hydrogen-bonding interface in the interior of the duplex. In the single-stranded oligonucleotides I and II, the strikingly different selectivities of adduct formation are attributed to the formation of noncovalent preassociation complexes that favor reaction geometries with C, rather than with A or G. Finally, the levels of several typical biomarkers of oxidative DNA damage (including 8-oxo-2′-deoxyguanosine) are formed in I in aqueous solutions with a yield at least 10 times smaller than the yield of cyclic 4-OHEN-dC adducts under identical reaction conditions.

AB - Equilenin, an important component of a widely prescribed hormone replacement formualtion for postmenopausal women, is metabolized by mammalian P450 enzymes to the catechol 4-hydroxyequilenin (4-OHEN). The oxidized o-quinone derivative of 4-OHEN is known to form cyclic covalent adducts with DNA [Bolton, J. (1998) Chem. Res. Toxicol. 11, 1113] in vitro and in vivo. The characteristics of 4-OHEN-DNA adduct formation were investigated with the oligonucleotides 5′-d(CCATCGCTACC) (I), its complementary strand 5′-d(GGTAGCGATGG) (II), one rich in C and the other in G, and the duplexes I·II. The identities of the modified bases were elucidated in terms of four stereoisomeric 4-OHEN-2′-deoxynucleoside standards described earlier [Shen et al. (2001) Chem. Res. Toxicol. 11, 94; Embrechts et al. J. Mass Spectrom. 36, 317]. The reactions of 4-OHEN with C are favored overwhelmingly in both single-stranded I and II with no guanine adducts observed in either case, and only minor proportions of A adducts were detected in sequence II. However, guanine adducts are observed in oligonucleotides that contain only G and unreactive T residues. The relative levels of cyclic covalent adducts observed in single-stranded I, II, and duplex I·II are ∼54:21:5, with only the end C groups in I modified in the I·II duplex. When 4-OHEN is reacted with calf thymus DNA, the reaction yield of cyclic adducts is more than ∼103-fold lower than in I. The cyclic 4-OHEN adducts lead to a pronounced thermal destabilization of duplexes I·II. Overall, cyclic adduct formation is markedly dependent on the sequence context and secondary structure of the DNA. The latter effect is attributed to the poor accessibilities of 4-OHEN to the reactive nucleotide Watson-Crick hydrogen-bonding interface in the interior of the duplex. In the single-stranded oligonucleotides I and II, the strikingly different selectivities of adduct formation are attributed to the formation of noncovalent preassociation complexes that favor reaction geometries with C, rather than with A or G. Finally, the levels of several typical biomarkers of oxidative DNA damage (including 8-oxo-2′-deoxyguanosine) are formed in I in aqueous solutions with a yield at least 10 times smaller than the yield of cyclic 4-OHEN-dC adducts under identical reaction conditions.

UR - http://www.scopus.com/inward/record.url?scp=27644463404&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=27644463404&partnerID=8YFLogxK

U2 - 10.1021/tx050190x

DO - 10.1021/tx050190x

M3 - Article

VL - 18

SP - 1737

EP - 1747

JO - Chemical Research in Toxicology

JF - Chemical Research in Toxicology

SN - 0893-228X

IS - 11

ER -