Human FEN-1 can process the 5'-flap DNA of CTG/CAG triplet repeat derived from human genetic diseases by length and sequence dependent manner.
Trinucleotide repeat (TNR) instability can cause a variety of human genetic diseases including myotonic dystrophy and Huntington's disease. Recent genetic data show that instability of the CAG/CTG repeat DNA is dependent on its length and replication origin. In yeast, the RAD27 (human FEN-1 homologue) null mutant has a high expansion frequency at the TNR loci. We demonstrate here that FEN-1 processes the 5'-flap DNA of CTG/CAG repeats, which is dependent on the length in vitro. FEN-1 protein can cleave the 5'-flap DNA containing triplet repeating sequence up to 21 repeats, but the activity decreases with increasing size of flap above 11 repeats. In addition, FEN-1 processing of 5'-flap DNA depends on sequence, which play a role in the replication origin-dependent TNR instability. Interestingly, FEN-1 can cleave the 5'-flap DNA of CTG repeats better than CAG repeats possibly through the flap-structure. Our biochemical data of FEN-1's activity with triplet repeat DNA clearly shows length dependence, and aids our understanding on the mechanism of TNR instability.
Lee
Suman
S
Genome Research Center for Reproductive Medicine and Infertility, CHA General Hospital, College of Medicine, Pochon University, Seoul, Korea. suman@cha.ac.kr
Park
Min S
MS
D001483:Base Sequence; D004277:DNA, Single-Stranded / Q000378:metabolism*; D004706:Endodeoxyribonucleases / Q000235:genetics / Q000378:metabolism*; D045585:Flap Endonucleases; D005786:Gene Expression Regulation; D030342:Genetic Diseases, Inborn / Q000235:genetics*; D006801:Humans; D009690:Nucleic Acid Conformation; D019680:Trinucleotide Repeat Expansion; D018911:Trinucleotide Repeats
D004277:DNA, Single-Stranded; D004706:Endodeoxyribonucleases; D045585:Flap Endonucleases; C468317:FEN1 protein, human