Cross-linking to an interrupted polypurine sequence with a platinum-modified triplex-forming oligonucleotide

Meghan A. Campbell, Paul S. Miller

Research output: Contribution to journalArticle

Abstract

Triplex-forming oligonucleotides (TFOs) can bind specifically to polypurine sequences in double-stranded DNA. A single interruption of this polypurine tract can greatly destabilize triplex formation. The stability of triplexes can be significantly enhanced by covalently linking the TFO to its DNA target with reactive functional groups conjugated to the TFO. Covalently cross-linked TFOs are effective inhibitors of transcription of the target DNA sequence. We have designed a TFO with a platinum-modified base that can interact with and cross-link to a cytosine interruption in the polypurine tract of a target DNA duplex. The TFO contains an N 4-(aminoalkyl)cytosine derivatized with cis-diamminediaquaplatinum(II) or trans-diamminediaquaplatinum(II). When bound to its target, the tethered platinum of the TFO can reach across the major groove and form an adduct with the guanine N7 of the interrupting C•G base pair. The optimal tether length is five methylene groups, and cross-linking is most efficient when the tether is modified with trans-diamminediaquaplatinum(II) . Cross-linking requires that the TFO is bound to its designated DNA target. Addition of cyanide to the cross-linked TFO product reversed the cross-link, behavior that is consistent with the presence of a platinum-guanine adduct. The kinetics of the cross-linking reaction were studied and the half-life of the cross-linking reaction was approximately 3 h. Our results demonstrate that platinum-conjugated TFOs can be designed to cross-link with DNA targets that contain a single pyrimidine interruption. Modifications of this type may prove useful for expanding the DNA sequences that can be targeted by TFOs and increasing the stability of the resulting triplexes.

Original languageEnglish (US)
Pages (from-to)873-881
Number of pages9
JournalJournal of Biological Inorganic Chemistry
Volume14
Issue number6
DOIs
StatePublished - 2009

Fingerprint

Platinum
Oligonucleotides
DNA
DNA sequences
Cytosine
Cross Reactions
Guanine
Cyanides
Transcription
Base Pairing
Functional groups
Half-Life
Kinetics

Keywords

  • Cisplatin
  • Cross-link
  • Pyrimidine interruption
  • Triplex-forming oligonucleotide

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry

Cite this

Cross-linking to an interrupted polypurine sequence with a platinum-modified triplex-forming oligonucleotide. / Campbell, Meghan A.; Miller, Paul S.

In: Journal of Biological Inorganic Chemistry, Vol. 14, No. 6, 2009, p. 873-881.

Research output: Contribution to journalArticle

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AB - Triplex-forming oligonucleotides (TFOs) can bind specifically to polypurine sequences in double-stranded DNA. A single interruption of this polypurine tract can greatly destabilize triplex formation. The stability of triplexes can be significantly enhanced by covalently linking the TFO to its DNA target with reactive functional groups conjugated to the TFO. Covalently cross-linked TFOs are effective inhibitors of transcription of the target DNA sequence. We have designed a TFO with a platinum-modified base that can interact with and cross-link to a cytosine interruption in the polypurine tract of a target DNA duplex. The TFO contains an N 4-(aminoalkyl)cytosine derivatized with cis-diamminediaquaplatinum(II) or trans-diamminediaquaplatinum(II). When bound to its target, the tethered platinum of the TFO can reach across the major groove and form an adduct with the guanine N7 of the interrupting C•G base pair. The optimal tether length is five methylene groups, and cross-linking is most efficient when the tether is modified with trans-diamminediaquaplatinum(II) . Cross-linking requires that the TFO is bound to its designated DNA target. Addition of cyanide to the cross-linked TFO product reversed the cross-link, behavior that is consistent with the presence of a platinum-guanine adduct. The kinetics of the cross-linking reaction were studied and the half-life of the cross-linking reaction was approximately 3 h. Our results demonstrate that platinum-conjugated TFOs can be designed to cross-link with DNA targets that contain a single pyrimidine interruption. Modifications of this type may prove useful for expanding the DNA sequences that can be targeted by TFOs and increasing the stability of the resulting triplexes.

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