title: Human exonuclease 1 (EXO1) activity characterization and its function on flap structures.
abstract: Human exonuclease 1 (EXO1) is involved in multiple DNA metabolism processes, including DNA repair and replication. Most of the fundamental roles of EXO1 have been described in yeast. Here, we report a biochemical characterization of human full-length EXO1. Prior to assay EXO1 on different DNA flap structures, we determined factors essential for the thermodynamic stability of EXO1. We show that enzymatic activity and stability of EXO1 on DNA is modulated by temperature. By characterization of EXO1 flap activity using various DNA flap substrates, we show that EXO1 has a strong capacity for degrading double stranded DNA and has a modest endonuclease or 5' flap activity. Furthermore, we report novel mechanistic insights into the processing of flap structures, showing that EXO1 preferentially cleaves one nucleotide inwards in a double stranded region of a forked and nicked DNA flap substrates, suggesting a possible role of EXO1 in strand displacement.
authors.affiliation: Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Denmark lenera@sund.ku.dk guido@sund.ku.dk.
authors.forename: Guido
authors.initials: G
authors.lastname: Keijzers
authors.affiliation: Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Denmark Laboratory of Molecular Gerontology, National Institute on Aging, U.S.A.
authors.forename: Vilhelm A
authors.initials: VA
authors.lastname: Bohr
authors.affiliation: Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Denmark lenera@sund.ku.dk guido@sund.ku.dk.
authors.forename: Lene Juel
authors.initials: LJ
authors.lastname: Rasmussen
mesh_terms: D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D045643:DNA Repair Enzymes / Q000737:chemistry* / Q000378:metabolism*; D004795:Enzyme Stability; D005090:Exodeoxyribonucleases / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D009690:Nucleic Acid Conformation; D013379:Substrate Specificity; D013696:Temperature; D013816:Thermodynamics
chemical_list: D004247:DNA; C114331:EXO1 protein, human; D005090:Exodeoxyribonucleases; D045643:DNA Repair Enzymes
keywords: EXO1; double stranded breaks; flap activity; strand displacement; threading; tracking