title: Nucleolar localization and dynamic roles of flap endonuclease 1 in ribosomal DNA replication and damage repair.
abstract: Despite the wealth of information available on the biochemical functions and our recent findings of its roles in genome stability and cancer avoidance of the structure-specific flap endonuclease 1 (FEN1), its cellular compartmentalization and dynamics corresponding to its involvement in various DNA metabolic pathways are not yet elucidated. Several years ago, we demonstrated that FEN1 migrates into the nucleus in response to DNA damage and under certain cell cycle conditions. In the current paper, we found that FEN1 is superaccumulated in the nucleolus and plays a role in the resolution of stalled DNA replication forks formed at the sites of natural replication fork barriers. In response to UV irradiation and upon phosphorylation, FEN1 migrates to nuclear plasma to participate in the resolution of UV cross-links on DNA, most likely employing its concerted action of exonuclease and gap-dependent endonuclease activities. Based on yeast complementation experiments, the mutation of Ser(187)Asp, mimicking constant phosphorylation, excludes FEN1 from nucleolar accumulation. The replacement of Ser(187) by Ala, eliminating the only phosphorylation site, retains FEN1 in nucleoli. Both of the mutations cause UV sensitivity, impair cellular UV damage repair capacity, and decline overall cellular survivorship.
authors.affiliation: Department of Radiation Biology, City of Hope National Medical Center and Beckman Research Institute, 1500 East Duarte Road, Duarte, CA 91010, USA.
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Guo
authors.forename: Limin
authors.initials: L
authors.lastname: Qian
authors.forename: Ren
authors.initials: R
authors.lastname: Liu
authors.forename: Huifang
authors.initials: H
authors.lastname: Dai
authors.forename: Mian
authors.initials: M
authors.lastname: Zhou
authors.forename: Li
authors.initials: L
authors.lastname: Zheng
authors.forename: Binghui
authors.initials: B
authors.lastname: Shen
mesh_terms: D002466:Cell Nucleolus / Q000201:enzymology* / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair / Q000528:radiation effects; D004261:DNA Replication / Q000528:radiation effects; D004275:DNA, Ribosomal / Q000096:biosynthesis*; D045585:Flap Endonucleases / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation / Q000528:radiation effects; D021381:Protein Transport / Q000528:radiation effects; D012694:Serine / Q000378:metabolism; D013379:Substrate Specificity / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D004275:DNA, Ribosomal; D050505:Mutant Proteins; D012694:Serine; D045585:Flap Endonucleases