Acquired genetic mutations underlie all forms of cancer and are likely to be important in aging. DNA damage, a major cause of mutations, can occur on one DNA strand or both strands; in the latter case, a double-strand DNA break results. The two forms of double-strand break repair in multicellular eukaryotes are homologous recombination (HR) and nonhomologous DNA end joining (NHEJ). This proposal is devoted to understanding the NHEJ pathway at the biochemical and genetic levels. The NHEJ pathway is the major pathway for repairing double-strand DNA breaks during G0, G1, and early S phases of the cell cycle; therefore, the understanding of NHEJ is of broad medical importance. The major effort of this proposal is to understand the biochemistry of key steps in the NHEJ pathway and to reconstitute the pathway with biochemically purified proteins.
In Specific Aim 1, we test four hypotheses related to the earliest steps in NHEJ. In the first, we examine whether Ku recruits the Artemis:DNA-PKcs complex to a DNA end. In the second, we examine the point at which inositol phosphates might regulate NHEJ. In the third, we examine how protein phosphorylation affects the initial complex of proteins that are thought to bind at a broken DNA end. In the fourth, we use a murine mouse model to test for interference between proteins in the early phase of the NHEJ pathway.
In Specific Aim 2, we examine how two broken DNA ends are brought into physicial proximity. Specifically, we test whether this can be achieved by the Ku:Artemis:DNAPKcs complex.
In Specific Aim 3, we describe efforts to reconstitute the entire human NHEJ pathway using purified proteins. As part of this aim, we also test for roles of DNA polymerases, which are the one type of enzymatic activity yet to be definitively determined for NHEJ in higher eukaryotes.
Specific Aim 4 is directed at defining the active site for the major nuclease in the NHEJ pathway, Artemis.
This aim i s also directed at understanding the region of interaction between Artemis and DNA-PKcs. Overall, this proposal represents a major concerted effort to deepen and complete our understanding of this primary pathway of repairing double-strand DNA breaks. The long-term medical benefit of a biochemically-defined NHEJ system includes the ability to test small molecule drug inhibitors for roles in cancer therapy. ? ?

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA100504-06
Application #
7475161
Study Section
Radiation Study Section (RAD)
Program Officer
Pelroy, Richard
Project Start
2003-08-01
Project End
2010-07-31
Budget Start
2008-08-01
Budget End
2010-07-31
Support Year
6
Fiscal Year
2008
Total Cost
$307,596
Indirect Cost
Name
University of Southern California
Department
Pathology
Type
Schools of Medicine
DUNS #
072933393
City
Los Angeles
State
CA
Country
United States
Zip Code
90089
Pannunzio, Nicholas R; Lieber, Michael R (2018) Concept of DNA Lesion Longevity and Chromosomal Translocations. Trends Biochem Sci 43:490-498
Reid, Dylan A; Conlin, Michael P; Yin, Yandong et al. (2017) Bridging of double-stranded breaks by the nonhomologous end-joining ligation complex is modulated by DNA end chemistry. Nucleic Acids Res 45:1872-1878
Pannunzio, Nicholas R; Lieber, Michael R (2017) AID and Reactive Oxygen Species Can Induce DNA Breaks within Human Chromosomal Translocation Fragile Zones. Mol Cell 68:901-912.e3
Conlin, Michael P; Reid, Dylan A; Small, George W et al. (2017) DNA Ligase IV Guides End-Processing Choice during Nonhomologous End Joining. Cell Rep 20:2810-2819
Pannunzio, Nicholas R; Lieber, Michael R (2016) RNA Polymerase Collision versus DNA Structural Distortion: Twists and Turns Can Cause Break Failure. Mol Cell 62:327-334
Chang, Howard H Y; Lieber, Michael R (2016) Structure-Specific nuclease activities of Artemis and the Artemis: DNA-PKcs complex. Nucleic Acids Res 44:4991-7
Pannunzio, Nicholas R; Lieber, Michael R (2016) Dissecting the Roles of Divergent and Convergent Transcription in Chromosome Instability. Cell Rep 14:1025-1031
Reid, Dylan A; Keegan, Sarah; Leo-Macias, Alejandra et al. (2015) Organization and dynamics of the nonhomologous end-joining machinery during DNA double-strand break repair. Proc Natl Acad Sci U S A 112:E2575-84
Lu, Zhengfei; Pannunzio, Nicholas R; Greisman, Harvey A et al. (2015) Convergent BCL6 and lncRNA promoters demarcate the major breakpoint region for BCL6 translocations. Blood 126:1730-1
Li, Sicong; Chang, Howard H; Niewolik, Doris et al. (2014) Evidence that the DNA endonuclease ARTEMIS also has intrinsic 5'-exonuclease activity. J Biol Chem 289:7825-34

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