Unwinding and hydrodynamic flow linear dichroism characteristics of supercoiled DNA covalently modified with two isomeric methylchrysene diol epoxides of different biological activities

Luisa Balasta, Rong Xu, Nicholas Geacintov, Charles E. Swenberg, Shantu Amin, Stephen S. Hecht

Research output: Contribution to journalArticle

Abstract

Adducts derived from the covalent binding of two positional monomethyl-substituted isomers of a bay region chrysene diol epoxide to supercoiled pIBI30 DNA (2926 base pairs/genome) were prepared, and their characteristics were investigated by a combination of gel electrophoresis and flow linear dichroism techniques. The 5- and 6-methyl derivatives of trans-1,2-dihydroxy-anti-3,4-epoxy-1,2,3,4-tetrahydrochrysene [(+)-5- and (+)-6-MeCDE, respectively], both with 1R,2S,3S,4R stereochemistry, are characterized by significant differences in their biological activities [Melikian et al. (1988) Cancer Res. 48, 1781-1787]. When covalently bound to plasmid DNA, these two molecules give rise to striking differences in the gel electrophoretic and flow hydrodynamic characteristics of the modified supercoiled DNA. The hydrodynamic flow linear dichroism of linearized DNA molecules (obtained by EcoRI enzyme digestion of covalently closed supercoiled pIBI30 DNA), modified covalently with the highly tumorigenic and mutagenic (+)-5-MeCDE derivative, indicates that flexible joints, bends, or kinks are formed at the site of binding of (+)-5-MeCDE. Slab gel data, as well as ethidium bromide-titration tube agarose gel electrophoresis data, indicate that the formation of (+)-5-MeCDE-DNA lesions causes the removal of superhelical turns with an unwinding angle of 13 ± 3° per covalently bound polycyclic aromatic residue. In contrast, the biological inactive (+)-6-MeCDE does not significantly alter the characteristics of supercoiled DNA, the unwinding angle is only 2.7 ± 1°, and the changes in persistence lengths detected by the flow linear dichroism technique are significantly smaller than in the case of (+)-5-MeCDE-DNA adducts. The observed differences in unwinding effects and alterations in persistence lengths induced by the covalent binding of (+)-5-MeCDE and the (+)-6-MeCDE isomer parallel those observed with DNA adducts derived from the covalent binding of the highly active (+)-trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydrobenzo-[a]pyrene [(+)-BPDE] isomer and its less active (-)-BPDE enantiomer to φX174 supercoiled DNA.

Original languageEnglish (US)
Pages (from-to)616-624
Number of pages9
JournalChemical Research in Toxicology
Volume6
Issue number5
StatePublished - 1993

Fingerprint

Superhelical DNA
Epoxy Compounds
Hydrodynamics
Bioactivity
7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide
Gels
Isomers
DNA Adducts
Electrophoresis
DNA
Derivatives
Stereochemistry
Molecules
Ethidium
Enantiomers
Titration
Agar Gel Electrophoresis
Sepharose
Plasmids
Base Pairing

ASJC Scopus subject areas

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

Cite this

Unwinding and hydrodynamic flow linear dichroism characteristics of supercoiled DNA covalently modified with two isomeric methylchrysene diol epoxides of different biological activities. / Balasta, Luisa; Xu, Rong; Geacintov, Nicholas; Swenberg, Charles E.; Amin, Shantu; Hecht, Stephen S.

In: Chemical Research in Toxicology, Vol. 6, No. 5, 1993, p. 616-624.

Research output: Contribution to journalArticle

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abstract = "Adducts derived from the covalent binding of two positional monomethyl-substituted isomers of a bay region chrysene diol epoxide to supercoiled pIBI30 DNA (2926 base pairs/genome) were prepared, and their characteristics were investigated by a combination of gel electrophoresis and flow linear dichroism techniques. The 5- and 6-methyl derivatives of trans-1,2-dihydroxy-anti-3,4-epoxy-1,2,3,4-tetrahydrochrysene [(+)-5- and (+)-6-MeCDE, respectively], both with 1R,2S,3S,4R stereochemistry, are characterized by significant differences in their biological activities [Melikian et al. (1988) Cancer Res. 48, 1781-1787]. When covalently bound to plasmid DNA, these two molecules give rise to striking differences in the gel electrophoretic and flow hydrodynamic characteristics of the modified supercoiled DNA. The hydrodynamic flow linear dichroism of linearized DNA molecules (obtained by EcoRI enzyme digestion of covalently closed supercoiled pIBI30 DNA), modified covalently with the highly tumorigenic and mutagenic (+)-5-MeCDE derivative, indicates that flexible joints, bends, or kinks are formed at the site of binding of (+)-5-MeCDE. Slab gel data, as well as ethidium bromide-titration tube agarose gel electrophoresis data, indicate that the formation of (+)-5-MeCDE-DNA lesions causes the removal of superhelical turns with an unwinding angle of 13 ± 3° per covalently bound polycyclic aromatic residue. In contrast, the biological inactive (+)-6-MeCDE does not significantly alter the characteristics of supercoiled DNA, the unwinding angle is only 2.7 ± 1°, and the changes in persistence lengths detected by the flow linear dichroism technique are significantly smaller than in the case of (+)-5-MeCDE-DNA adducts. The observed differences in unwinding effects and alterations in persistence lengths induced by the covalent binding of (+)-5-MeCDE and the (+)-6-MeCDE isomer parallel those observed with DNA adducts derived from the covalent binding of the highly active (+)-trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydrobenzo-[a]pyrene [(+)-BPDE] isomer and its less active (-)-BPDE enantiomer to φX174 supercoiled DNA.",
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T1 - Unwinding and hydrodynamic flow linear dichroism characteristics of supercoiled DNA covalently modified with two isomeric methylchrysene diol epoxides of different biological activities

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AU - Hecht, Stephen S.

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