Promoter G-quadruplex sequences are targets for base oxidation and strand cleavage during hypoxia-induced transcription

David W. Clark, Tzu Phang, Michael G. Edwards, Mark W. Geraci, Mark N. Gillespie

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

The G-quadruplex, a non-B DNA motif that forms in certain G-rich sequences, is often located near transcription start sites in growth regulatory genes. Multiple lines of evidence show that reactive oxygen species generated as second messengers during physiologic signaling target specific DNA sequences for oxidative base modifications. Because guanine repeats are uniquely sensitive to oxidative damage, and G4 sequences are known hot spots for genetic mutation and DNA translocation, we hypothesized that G4 sequences are targeted for oxidative base modifications in hypoxic signaling. Approximately 25% of hypoxia-regulated genes in pulmonary artery endothelial cells harbored G4 sequences within their promoters. Chromatin immunoprecipitation showed that common base oxidation product 8-oxoguanine was selectively introduced into G4s, in promoters of hypoxia up-, down-, and nonregulated genes. Additionally, base excision DNA repair (BER) enzymes were recruited, and transient strand breaks formed in these sequences. Transcription factor Sp1, constitutively bound to G4 sequences in normoxia, was evicted as 8-oxoguanine accumulated during hypoxic exposure. Blocking hypoxia-induced oxidant production prevented both base modifications and decreased Sp1 binding. These findings suggest that oxidant stress in hypoxia causes oxidative base modifications, recruitment of BER enzymes, and transient strand breaks in G4 promoter sequences potentially altering G4 integrity and function.

Original languageEnglish (US)
Pages (from-to)51-59
Number of pages9
JournalFree Radical Biology and Medicine
Volume53
Issue number1
DOIs
StatePublished - Jul 1 2012
Externally publishedYes

Fingerprint

G-Quadruplexes
Transcription
DNA Repair Enzymes
Genes
Oxidants
Oxidation
DNA Repair
Sp1 Transcription Factor
Transcription Initiation Site
DNA sequences
DNA
Endothelial cells
Guanine
Second Messenger Systems
Nucleotide Motifs
Chromatin
Chromatin Immunoprecipitation
Reactive Oxygen Species
Regulator Genes
Pulmonary Artery

Keywords

  • 8-Oxoguanine
  • Base excision repair
  • DNA base oxidation
  • G-quadruplex
  • Hypoxia

ASJC Scopus subject areas

  • Biochemistry
  • Physiology (medical)

Cite this

Promoter G-quadruplex sequences are targets for base oxidation and strand cleavage during hypoxia-induced transcription. / Clark, David W.; Phang, Tzu; Edwards, Michael G.; Geraci, Mark W.; Gillespie, Mark N.

In: Free Radical Biology and Medicine, Vol. 53, No. 1, 01.07.2012, p. 51-59.

Research output: Contribution to journalArticle

Clark, David W. ; Phang, Tzu ; Edwards, Michael G. ; Geraci, Mark W. ; Gillespie, Mark N. / Promoter G-quadruplex sequences are targets for base oxidation and strand cleavage during hypoxia-induced transcription. In: Free Radical Biology and Medicine. 2012 ; Vol. 53, No. 1. pp. 51-59.
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