Inhibition of FEN-1 processing by DNA secondary structure at trinucleotide repeats.
The mechanism by which trinucleotide expansion occurs in human genes is not understood. However, it has been hypothesized that DNA secondary structure may actively participate by preventing FEN-1 cleavage of displaced Okazaki fragments. We show here that secondary structure can, indeed, play a role in expansion by a FEN-1-dependent mechanism. Secondary structure inhibits flap processing at CAG, CGG, or CTG repeats in a length-dependent manner by concealing the 5' end of the flap that is necessary for both binding and cleavage by FEN-1. Thus, secondary structure can defeat the protective function of FEN-1, leading to site-specific expansions. However, when FEN-1 is absent from the cell, alternative pathways to simple inhibition of flap processing contribute to expansion.
Spiro
C
C
Department of Pharmacology, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
Pelletier
R
R
Rolfsmeier
M L
ML
Dixon
M J
MJ
Lahue
R S
RS
Gupta
G
G
Park
M S
MS
Chen
X
X
Mariappan
S V
SV
McMurray
C T
CT
D004247:DNA / Q000737:chemistry / Q000235:genetics*; D004706:Endodeoxyribonucleases / Q000235:genetics*; D045585:Flap Endonucleases; D005786:Gene Expression Regulation; D006801:Humans; D009690:Nucleic Acid Conformation; D018911:Trinucleotide Repeats / Q000235:genetics*
D004247:DNA; D004706:Endodeoxyribonucleases; D045585:Flap Endonucleases; C468317:FEN1 protein, human