A distinct triplex DNA unwinding activity of ChlR1 helicase.

Abstract

Mutations in the human ChlR1 (DDX11) gene are associated with a unique genetic disorder known as Warsaw breakage syndrome characterized by cellular defects in genome maintenance. The DNA triplex helix structures that form by Hoogsteen or reverse Hoogsteen hydrogen bonding are examples of alternate DNA structures that can be a source of genomic instability. In this study, we have examined the ability of human ChlR1 helicase to destabilize DNA triplexes. Biochemical studies demonstrated that ChlR1 efficiently melted both intermolecular and intramolecular DNA triplex substrates in an ATP-dependent manner. Compared with other substrates such as replication fork and G-quadruplex DNA, triplex DNA was a preferred substrate for ChlR1. Also, compared with FANCJ, a helicase of the same family, the triplex resolving activity of ChlR1 is unique. On the other hand, the mutant protein from a Warsaw breakage syndrome patient failed to unwind these triplexes. A previously characterized triplex DNA-specific antibody (Jel 466) bound triplex DNA structures and inhibited ChlR1 unwinding activity. Moreover, cellular assays demonstrated that there were increased triplex DNA content and double-stranded breaks in ChlR1-depleted cells, but not in FANCJ(-/-) cells, when cells were treated with a triplex stabilizing compound benzoquinoquinoxaline, suggesting that ChlR1 melting of triple-helix structures is distinctive and physiologically important to defend genome integrity. On the basis of our results, we conclude that the abundance of ChlR1 known to exist in vivo is likely to be a strong deterrent to the stability of triplexes that can potentially form in the human genome.

• Authors: Manhong Guo, Kristian Hundseth, Hao Ding, Venkatasubramanian Vidhyasagar, Akira Inoue, Chi-Hung Nguyen, Rula Zain, Jeremy S Lee, Yuliang Wu
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 290 Issue 8 Pg. 5174-5189 (Feb 20 2015) ISSN: 1083-351X [Electronic] United States
• PMID: 25561740 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Chemical References

• BACH1 protein, human
• Basic-Leucine Zipper Transcription Factors
• Fanconi Anemia Complementation Group Proteins
• DNA
• DNA Helicases
• DDX11 protein, human
• DEAD-box RNA Helicases

Topics

• Basic-Leucine Zipper Transcription Factors (genetics, metabolism)
• DEAD-box RNA Helicases (genetics, metabolism)
• DNA (genetics, metabolism)
• DNA Helicases (genetics, metabolism)
• DNA Repair-Deficiency Disorders (enzymology, genetics)
• Fanconi Anemia Complementation Group Proteins (genetics, metabolism)
• Genome, Human
• HEK293 Cells
• Humans