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

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• 作者：David W. Clark^a ; Tzu Phang^b ; Michael G. Edwards^b ; Mark W. Geraci^b ; Mark N. Gillespie^a ; ^{mgillesp@jaguar1.usouthal.edu}
• 关键词：G4 ; G-quadruplex ; 8-oxoG ; 8-oxoguanine ; BER ; base excision repair ; Avpr1a ; arginine vasopressin receptor 1a ; Brca2 ; breast cancer 2 ; Dusp10 ; dual specificity phosphatase 10 ; Smad6 ; mothers against DPP homolog 6 ; Mt1a ; metallothionein 1a ; Nfkb2 ; nuclear fa
• 刊名：Free Radical Biology and Medicine
• 出版年：2012
• 出版时间：1 July, 2012
• 年：2012
• 卷：53
• 期：1
• 页码：51-59
• 全文大小：443 K

文摘

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.