Appropriate implementation of Okazaki fragment maturation during DNA replication in eukaryotic cells is a fundamental mechanism for avoidance of mutations and genome stability. During lagging strand DNA synthesis, multiple RNA primers and immediately adjoined DNA-fragments are synthesized by primase (a hetero tetramer of a RNA polymerase and DNA Pol ). However, both of the enzymes lack a proof reading function, different from the other DNA polymerases. Therefore, this initial RNA-DNA fragment (alpha- segment of the Okazaki fragment) is highly mutagenic and has to be processed by nuclease complexes. This proposal aims to define detailed molecular mechanism for the nuclease-driven RNA primer processing in eukaryotic nuclei and mitochondria. For the last funding period, we have defined the roles of several nucleases in the processes, including S. cerevisiae RNase H(35), ScRad27 or human FEN1, and exonuclease-1, and mutagenic consequences when these nucleases are defective. We have also accumulated solid evidence to demonstrate that nuclease helicase DNA2 exclusively localizes into mitochondria, and plays a vital role in RNA primer removal during mitochondrial DNA replication. These novel exciting observations prompted us to develop new and additional specific aims in this renewal application. The current proposal focuses to test a central hypothesis that 1-segment processing is a vital part of cellular mechanisms to maintain genomic integrity and prevent mutagenic stresses due to intrinsic DNA sequence obstacles and exogenous insults. Deficiency of this integrative machinery could lead to a high incidence of mutagenesis and carcinogenesis. We will further define detailed molecular mechanisms for the nuclease-driven """"""""1-segment"""""""" processing in Okazaki fragment maturation in yeast and mammalian cell systems, during replication of normal DNA sequence and repetitive DNA sequence regions, in the nucleus as well as the mitochondrion. Through a series of vigorous systematic analyses, we intend to obtain a high resolution image of how these nuclease complexes collectively work towards RNA primer processing in different scenarios and to relate in vitro and in vivo data using yeast and mammalian systems, including human cell lines and transgenic mice. Information made available from this systematic study will establish a relationship between this mechanism, unique mutagenic phenotype(s), and development of cancers.

Public Health Relevance

The current application aims to test whether 1-segment processing is a vital part of the cellular mechanism for maintaining genomic integrity and for preventing mutagenic stresses and cancers. The proposed studies should lead to advances in our understanding of early events and molecular mechanism of many cancer predispositions. The information made available via these studies will be useful in developing new strategies for cancer prevention and treatment.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA085344-12
Application #
8009881
Study Section
Cancer Etiology Study Section (CE)
Program Officer
Okano, Paul
Project Start
1999-07-01
Project End
2013-11-30
Budget Start
2010-12-01
Budget End
2011-11-30
Support Year
12
Fiscal Year
2011
Total Cost
$258,686
Indirect Cost
Name
City of Hope/Beckman Research Institute
Department
Type
DUNS #
027176833
City
Duarte
State
CA
Country
United States
Zip Code
91010
Li, Zhengke; Liu, Bochao; Jin, Weiwei et al. (2018) hDNA2 nuclease/helicase promotes centromeric DNA replication and genome stability. EMBO J 37:
Xu, Xiaoliang L; Li, Zhengke; Liu, Aihong et al. (2017) SKP2 Activation by Thyroid Hormone Receptor ?2 Bypasses Rb-Dependent Proliferation in Rb-Deficient Cells. Cancer Res 77:6838-6850
Sun, H; He, L; Wu, H et al. (2017) The FEN1 L209P mutation interferes with long-patch base excision repair and induces cellular transformation. Oncogene 36:194-207
Zheng, Li; Jia, Jia; Dai, Huifang et al. (2017) Triptolide-Assisted Phosphorylation of p53 Suppresses Inflammation-Induced NF-?B Survival Pathways in Cancer Cells. Mol Cell Biol 37:
Chu, Fong-Fong; Esworthy, R Steven; Doroshow, James H et al. (2017) Deficiency in Duox2 activity alleviates ileitis in GPx1- and GPx2-knockout mice without affecting apoptosis incidence in the crypt epithelium. Redox Biol 11:144-156
Zhang, Shirong; Wu, Kan; Feng, Jianguo et al. (2016) Epigenetic therapy potential of suberoylanilide hydroxamic acid on invasive human non-small cell lung cancer cells. Oncotarget 7:68768-68780
Chu, Fong-Fong; Esworthy, R Steven; Doroshow, James H et al. (2016) NADPH oxidase-1 deficiency offers little protection in Salmonella typhimurium-induced typhlitis in mice. World J Gastroenterol 22:10158-10165
Pan, Xiao; Cang, Xiaohui; Dan, Songsong et al. (2016) Site-specific Disruption of the Oct4/Sox2 Protein Interaction Reveals Coordinated Mesendodermal Differentiation and the Epithelial-Mesenchymal Transition. J Biol Chem 291:18353-69
Liu, Wenpeng; Zhou, Mian; Li, Zhengke et al. (2016) A Selective Small Molecule DNA2 Inhibitor for Sensitization of Human Cancer Cells to Chemotherapy. EBioMedicine 6:73-86
Zhou, Ting; Pan, Feiyan; Cao, Yan et al. (2016) R152C DNA Pol ? mutation impairs base excision repair and induces cellular transformation. Oncotarget 7:6902-15

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