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DHX9 helicase is involved in preventing genomic instability induced by alternatively structured DNA in human cells.

Abstract
Sequences that have the capacity to adopt alternative (i.e. non-B) DNA structures in the human genome have been implicated in stimulating genomic instability. Previously, we found that a naturally occurring intra-molecular triplex (H-DNA) caused genetic instability in mammals largely in the form of DNA double-strand breaks. Thus, it is of interest to determine the mechanism(s) involved in processing H-DNA. Recently, we demonstrated that human DHX9 helicase preferentially unwinds inter-molecular triplex DNA in vitro. Herein, we used a mutation-reporter system containing H-DNA to examine the relevance of DHX9 activity on naturally occurring H-DNA structures in human cells. We found that H-DNA significantly increased mutagenesis in small-interfering siRNA-treated, DHX9-depleted cells, affecting mostly deletions. Moreover, DHX9 associated with H-DNA in the context of supercoiled plasmids. To further investigate the role of DHX9 in the recognition/processing of H-DNA, we performed binding assays in vitro and chromatin immunoprecipitation assays in U2OS cells. DHX9 recognized H-DNA, as evidenced by its binding to the H-DNA structure and enrichment at the H-DNA region compared with a control region in human cells. These composite data implicate DHX9 in processing H-DNA structures in vivo and support its role in the overall maintenance of genomic stability at sites of alternatively structured DNA.
AuthorsAklank Jain, Albino Bacolla, Imee M Del Mundo, Junhua Zhao, Guliang Wang, Karen M Vasquez
JournalNucleic acids research (Nucleic Acids Res) Vol. 41 Issue 22 Pg. 10345-57 (Dec 2013) ISSN: 1362-4962 [Electronic] England
PMID24049074 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)
Chemical References
  • Neoplasm Proteins
  • triplex DNA
  • DNA
  • DHX9 protein, human
  • DEAD-box RNA Helicases
Topics
  • Cell Line, Tumor
  • DEAD-box RNA Helicases (metabolism, physiology)
  • DNA (chemistry, metabolism)
  • Genomic Instability
  • Humans
  • Mutation
  • Neoplasm Proteins (metabolism, physiology)
  • Nucleic Acid Conformation
  • Plasmids (genetics)

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