DHX9 helicase is involved in preventing genomic instability induced by alternatively structured DNA in human cells.
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.
Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Dell Pediatric Research Institute, 1400 Barbara Jordan Blvd. Austin, TX 78723, USA.
Aklank
A
Jain
Albino
A
Bacolla
Imee M
IM
Del Mundo
Junhua
J
Zhao
Guliang
G
Wang
Karen M
KM
Vasquez
D045744:Cell Line, Tumor; D053487:DEAD-box RNA Helicases / Q000378:metabolism* / Q000502:physiology; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D042822:Genomic Instability; D006801:Humans; D009154:Mutation; D009363:Neoplasm Proteins / Q000378:metabolism* / Q000502:physiology; D009690:Nucleic Acid Conformation; D010957:Plasmids / Q000235:genetics
D009363:Neoplasm Proteins; C051802:triplex DNA; D004247:DNA; C098487:DHX9 protein, human; D053487:DEAD-box RNA Helicases