title: Nuclease-deficient FEN-1 blocks Rad51/BRCA1-mediated repair and causes trinucleotide repeat instability.
abstract: Previous studies have shown that expansion-prone repeats form structures that inhibit human flap endonuclease (FEN-1). We report here that faulty processing by FEN-1 initiates repeat instability in mammalian cells. Disease-length CAG tracts in Huntington's disease mice heterozygous for FEN-1 display a tendency toward expansions over contractions during intergenerational inheritance compared to those in homozygous wild-type mice. Further, with regard to human cells expressing a nuclease-defective FEN-1, we provide direct evidence that an unprocessed FEN-1 substrate is a precursor to instability. In cells with no endogenous defects in DNA repair, exogenous nuclease-defective FEN-1 causes repeat instability and aberrant DNA repair. Inefficient flap processing blocks the formation of Rad51/BRCA1 complexes but invokes repair by other pathways.
authors.affiliation: Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
authors.forename: Craig
authors.initials: C
authors.lastname: Spiro
authors.forename: Cynthia T
authors.initials: CT
authors.lastname: McMurray
mesh_terms: D000818:Animals; D019313:BRCA1 Protein / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D016923:Cell Death / Q000502:physiology; D002478:Cells, Cultured; D002945:Cisplatin / Q000494:pharmacology; D004260:DNA Repair / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D004706:Endodeoxyribonucleases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D045585:Flap Endonucleases; D006579:Heterozygote; D006801:Humans; D006816:Huntington Disease / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D051135:Rad51 Recombinase; D019680:Trinucleotide Repeat Expansion; D018911:Trinucleotide Repeats
chemical_list: D019313:BRCA1 Protein; D004268:DNA-Binding Proteins; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; C495154:Rad51 protein, mouse; D004706:Endodeoxyribonucleases; D045585:Flap Endonucleases; C468317:FEN1 protein, human; D002945:Cisplatin