Identification of specific nonbridging phosphate oxygens important for DNA cleavage by human topoisomerase I

Rong Gao, Christopher D. Claeboe, Brian M. Eisenhauer, Sidney Hecht

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Methylphosphonate-bearing oligonucleotides are characterized by the replacement of one of the nonbridging oxygen atoms with a methyl group. While neutralizing the negative charge associated with the phosphodiester at the point of substitution, the methyl group also imparts chirality to the phosphorus atom. Herein we report the synthesis of a number of oligonucleotides containing isomerically pure S p and R p methylphosphonates at single positions for the purpose of investigating the hydrogen-bonding contacts necessary for human topoisomerase I function. It was possible to correlate these data to the recent X-ray crystal structure of a truncated form of the enzyme and demonstrate a severe decrease of cleavage efficiency when any of the nonbridging oxygen atoms upstream from the cleavage site was removed. Also observed was increased cleavage for oligonucleotides substituted with methylphosphonates downstream from the cleavage site. These effects were shown to be due primarily to alteration of the binding of the modified DNA substrates by human DNA topoisomerase I.

Original languageEnglish (US)
Pages (from-to)6167-6181
Number of pages15
JournalBiochemistry
Volume43
Issue number20
DOIs
StatePublished - May 25 2004
Externally publishedYes

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Type I DNA Topoisomerase
DNA Cleavage
Oligonucleotides
Phosphates
Oxygen
Atoms
DNA
Bearings (structural)
Chirality
Hydrogen Bonding
Phosphorus
Hydrogen bonds
Substitution reactions
Crystal structure
X-Rays
X rays
Substrates
Enzymes
methylphosphonic acid

ASJC Scopus subject areas

  • Biochemistry

Cite this

Identification of specific nonbridging phosphate oxygens important for DNA cleavage by human topoisomerase I. / Gao, Rong; Claeboe, Christopher D.; Eisenhauer, Brian M.; Hecht, Sidney.

In: Biochemistry, Vol. 43, No. 20, 25.05.2004, p. 6167-6181.

Research output: Contribution to journalArticle

Gao, Rong ; Claeboe, Christopher D. ; Eisenhauer, Brian M. ; Hecht, Sidney. / Identification of specific nonbridging phosphate oxygens important for DNA cleavage by human topoisomerase I. In: Biochemistry. 2004 ; Vol. 43, No. 20. pp. 6167-6181.
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