Mutagenic capacity of endogenous G4 DNA underlies genome instability in FANCJ-defective C. elegans.
To safeguard genetic integrity, cells have evolved an accurate but not failsafe mechanism of DNA replication. Not all DNA sequences tolerate DNA replication equally well [1]. Also, genomic regions that impose structural barriers to the DNA replication fork are a potential source of genetic instability [2, 3]. Here, we demonstrate that G4 DNA-a sequence motif that folds into quadruplex structures in vitro [4, 5]-is highly mutagenic in vivo and is removed from genomes that lack dog-1, the C. elegans ortholog of mammalian FANCJ [6, 7], which is mutated in Fanconi anemia patients [8-11]. We show that sequences that match the G4 DNA signature G3-5N1-3G3-5N1-3G3-5N1-3G3-5 are deleted in germ and somatic tissues of dog-1 animals. Unbiased aCGH analyses of dog-1 genomes that were allowed to accumulate mutations in >100 replication cycles indicate that deletions are found exclusively at G4 DNA; deletion frequencies can reach 4% per site per animal generation. We found that deletion sizes fall short of Okazaki fragment lengths [12], and no significant microhomology was observed at deletion junctions. The existence of 376,000 potentially mutagenic G4 DNA sites in the human genome could have major implications for the etiology of hereditary FancJ and nonhereditary cancers.
Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences & University Medical Centre Utrecht, Uppsalalaan 8, 3584 CT, Utrecht, The Netherlands.
Evelien
E
Kruisselbrink
Victor
V
Guryev
Karin
K
Brouwer
Daphne B
DB
Pontier
Edwin
E
Cuppen
Marcel
M
Tijsterman
D000818:Animals; D001483:Base Sequence; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics*; D017173:Caenorhabditis elegans / Q000235:genetics*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics; D004265:DNA Helicases / Q000235:genetics; D004261:DNA Replication; D051856:Fanconi Anemia Complementation Group Proteins / Q000235:genetics*; D054856:G-Quadruplexes; D042822:Genomic Instability; D009154:Mutation; D009693:Nucleic Acid Hybridization; D020411:Oligonucleotide Array Sequence Analysis; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion
D050976:Basic-Leucine Zipper Transcription Factors; D029742:Caenorhabditis elegans Proteins; D051856:Fanconi Anemia Complementation Group Proteins; D004265:DNA Helicases; C464789:Dog-1 protein, C elegans