Upon UV radiation or ionizing radiation, DNA replication forks can be stalled by inter-strand and intra-strand cross links. Stalled replication forks trigger assembly of the cellular DNA damage response machinery, which requires that some enzyme components of the DNA replication complex switch their physical locations, interaction partners and functions. One such component is FEN1 nuclease. Our preliminary data indicate that upon UV radiation, FEN1 switches from being a flap endonuclease for RNA primer removal and interacting with PCNA, to being a gap-dependent endonuclease for resolution of stalled DNA replication forks and interacting with WRN. This critical switch is mediated by a change in FEN1's post-translational modification (PTM) profile. These PTMs can act as a 'molecular barcode'that directs different FEN1-mediated protein- protein interactions to allow a switch of FEN1's functions. Disruption of the normal program of these PTMs may lead to uncontrolled cell growth and cancer. In this competitive renewal application, our goal is to establish a comprehensive relationship among genetic alterations, functional deficiency, and pathological consequences, using FEN1 nuclease as a model protein and transgenic mice as a model system. During the previous funding cycle we identified FEN1 mutations in cancer cells that eliminate the structural elements responsible for FEN1's nuclease activities, protein/protein interactions and PTMs. We also established corresponding knock-in mouse models that mimic the point mutations identified in human cancer, which enabled us to initially define the molecular and cellular events of tumorigenesis. These mouse models and our initial studies have prompted new aims to investigate the molecular mechanisms of FEN1mutation-mediated cancer pathogenesis caused by elevated mutagenesis during Okazaki fragment maturation and aberrant PTMs.
The Specific Aims i nclude: 1) To determine how FEN1-mediated 5'editing of ?-segment eliminates mispairs in Okazaki fragments and contributes to cancer avoidance. 2) To determine the role of FEN1/WRN complex in maintaining the stability of tandem repeat sequences and cancer avoidance. 3) To determine how UV radiation-induced post-translational modifications mediate a switch of FEN1's role from RNA primer removal to resolution of stalled replication forks. Successful completion of the proposed studies will generate important new knowledge about the function and regulation of FEN1 in maintenance of genome stabilities and cancer avoidance. In addition, the results are anticipated to have a high potential impact, as they may suggest new avenues for cancer prevention and development of new, personalized radiation and other therapeutic regimens for this life-threatening disease.

Public Health Relevance

The current application aims to establish a comprehensive relationship among genetic alterations, functional deficiency, and pathological consequences, using human FEN1 nuclease as a model protein and transgenic mice as a model system. Successful completion of the proposed studies will gain important new knowledge about the function and regulation of flap endonuclease-1 in maintenance of genome stabilities and cancer avoidance. The results will serve as a reference in cancer prevention and development of new therapeutic regimens and personalized medicine.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
2R01CA073764-16
Application #
8295773
Study Section
Radiation Therapeutics and Biology Study Section (RTB)
Program Officer
Okano, Paul
Project Start
1997-05-01
Project End
2017-05-31
Budget Start
2012-06-01
Budget End
2013-05-31
Support Year
16
Fiscal Year
2012
Total Cost
$325,031
Indirect Cost
$131,560
Name
City of Hope/Beckman Research Institute
Department
Type
DUNS #
027176833
City
Duarte
State
CA
Country
United States
Zip Code
91010
Sun, H; He, L; Wu, H et al. (2016) The FEN1 L209P mutation interferes with long-patch base excision repair and induces cellular transformation. Oncogene :
Zhang, Yijuan; Wen, Chunhong; Liu, Songbai et al. (2016) Shade avoidance 6 encodes an Arabidopsis flap endonuclease required for maintenance of genome integrity and development. Nucleic Acids Res 44:1271-84
Zhou, Lina; Dai, Huifang; Wu, Jian et al. (2016) Role of FEN1 S187 phosphorylation in counteracting oxygen-induced stress and regulating postnatal heart development. FASEB J :
Zhou, Ting; Pan, Feiyan; Cao, Yan et al. (2016) R152C DNA Pol β mutation impairs base excision repair and induces cellular transformation. Oncotarget 7:6902-15
Ali, Shafat; Zheng, Li; Shen, Binghui (2015) FEN1-mediated α-segment error editing during Okazaki fragment maturation. Cell Cycle 14:1767
Liu, Songbai; Lu, Guojun; Ali, Shafat et al. (2015) Okazaki fragment maturation involves α-segment error editing by the mammalian FEN1/MutSα functional complex. EMBO J 34:1829-43
Wang, Jianwei; Zhou, Lina; Li, Zhi et al. (2015) YY1 suppresses FEN1 over-expression and drug resistance in breast cancer. BMC Cancer 15:50
Chung, L; Onyango, D; Guo, Z et al. (2015) The FEN1 E359K germline mutation disrupts the FEN1-WRN interaction and FEN1 GEN activity, causing aneuploidy-associated cancers. Oncogene 34:902-11
Wang, Hailong; Li, Yongjiang; Truong, Lan N et al. (2014) CtIP maintains stability at common fragile sites and inverted repeats by end resection-independent endonuclease activity. Mol Cell 54:1012-21
Finger, L David; Atack, John M; Tsutakawa, Susan et al. (2012) The wonders of flap endonucleases: structure, function, mechanism and regulation. Subcell Biochem 62:301-26

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