The human genome is subject to constant attack by endogenous and environmental DNA damaging agents. If unrepaired, DNA lesions will give rise to mutations that in turn may lead to cancer formation. Fortunately, a complex network of DNA repair pathways operates to remove DNA lesions. To assess the biological significance of exposure to environmental DNA damaging agents, it is necessary to understand the details of the complex cellular response to DNA damage. Unlike the conserved LIG1 and LIG4 genes, lower eukaryotes lack a homolog of the mammalian LIG3 gene, which encodes at least three distinct polypeptides. Interestingly, the DNA ligase III?-associated proteins, poly (ADP-ribose) polymerase 1 (PARP-1), XRCC1 and DNA polymerase (Pol) ?, each of which have been implicated in base excision repair and the repair of DNA single strand breaks, are also found only in higher eukaryotes. Using a modified yeast two hybrid assay, we have identified a series of XRCC1 mutants that are defective in specific protein-protein interactions.
In Specific Aim 1, we will utilize these mutants to delineate the functional and biological consequences of protein-protein interactions between DNA ligase III?/XRCC1 and other proteins involved in base excision and single strand break repair. Recent studies have increased the repertoire of DNA repair transactions in which DNA ligase III?/XRCC1 participates.
In Specific Aim 2, we will determine how DNA ligase III?/XRCC1 is recruited to the DNA nucleotide excision repair machinery and whether this involves an interaction between XRCC1 and PCNA. In preliminary studies, we have identified an interaction between DNA ligase III?/XRCC1 and hRad50/hMre11/Nbs.
In Specific Aim 3, we will determine how DNA damage regulates this interaction and whether these proteins act together in an error-prone non-homologous end-joining sub pathway that repairs DNA double strand breaks. Interestingly, this error-prone pathway is up-regulated in cancer cells and may contribute to their characteristic genomic instability.
In Specific Aim 4, we will identify and characterize small molecule inhibitors of DNA ligase III. We envision that that these inhibitors will not only be valuable reagents for elucidating the cellular functions of the LIG3 gene products but also may serve as lead compounds for the development of novel anti-cancer agents.

Public Health Relevance

It is well established that genomic instability drives the progression from a normal cell into a cancer cell. Human cells have a complex network of pathways that act together to maintain genome stability. A mechanistic understanding of these pathways will provide fundamental insights into tumor suppression. In addition, genomic instability is a characteristic of tumor cells, indicating that there are differences in the pathways that normally maintain stability. These differences between normal and cancer cells offer an opportunity to develop therapeutic strategies that selectively target cancer cells.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Research Project (R01)
Project #
5R01ES012512-07
Application #
7843600
Study Section
Special Emphasis Panel (ZRG1-ONC-H (02))
Program Officer
Mcallister, Kimberly A
Project Start
2004-04-22
Project End
2014-02-28
Budget Start
2010-03-01
Budget End
2011-02-28
Support Year
7
Fiscal Year
2010
Total Cost
$300,713
Indirect Cost
Name
University of Maryland Baltimore
Department
Radiation-Diagnostic/Oncology
Type
Schools of Medicine
DUNS #
188435911
City
Baltimore
State
MD
Country
United States
Zip Code
21201
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Greco, George E; Matsumoto, Yoshihiro; Brooks, Rhys C et al. (2016) SCR7 is neither a selective nor a potent inhibitor of human DNA ligase IV. DNA Repair (Amst) 43:18-23
Sallmyr, Annahita; Matsumoto, Yoshihiro; Roginskaya, Vera et al. (2016) Inhibiting Mitochondrial DNA Ligase III? Activates Caspase 1-Dependent Apoptosis in Cancer Cells. Cancer Res 76:5431-41
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Ghezraoui, Hind; Piganeau, Marion; Renouf, Benjamin et al. (2014) Chromosomal translocations in human cells are generated by canonical nonhomologous end-joining. Mol Cell 55:829-842
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Tomkinson, Alan E; Sallmyr, Annahita (2013) Structure and function of the DNA ligases encoded by the mammalian LIG3 gene. Gene 531:150-7
Tomkinson, Alan E; Howes, Timothy R L; Wiest, Nathaniel E (2013) DNA ligases as therapeutic targets. Transl Cancer Res 2:
Della-Maria, Julie; Hegde, Muralidhar L; McNeill, Daniel R et al. (2012) The interaction between polynucleotide kinase phosphatase and the DNA repair protein XRCC1 is critical for repair of DNA alkylation damage and stable association at DNA damage sites. J Biol Chem 287:39233-44
Dey, Sanjib; Maiti, Amit K; Hegde, Muralidhar L et al. (2012) Increased risk of lung cancer associated with a functionally impaired polymorphic variant of the human DNA glycosylase NEIL2. DNA Repair (Amst) 11:570-8

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