The repair of alkylation damage to the genome is critical in all cells, because such damage is cytotoxic and potentially mutagenic. These repair pathways counteract endogenous and environmental alkylating agents. Alkylation chemotherapy is a major therapeutic modality for many tumors, underscoring the importance of these pathways in cancer. A number of different pathways exist for alkylation repair, which include base excision and nucleotide excision repair, direct reversal by methyl-guanine methyltransferase (MGMT), and dealkylation by the AlkB protein family. We recently demonstrated that one of the human AlkB homologues, ALKBH3, plays an important role in alkylation damage repair in specific tumor cells, but is dispensable for this function in nonmalignant cells. This suggests that alkylation repair enzymes may be differentially regulated in various cellular contexts. While much is known about the biochemical mechanisms that mediate DNA alkylation repair, we know very little about how these pathways are modulated, particularly in metazoans. We have recently discovered a critical role for the deubiquitinase OTUD4 in the regulation of MGMT and the AlkB family of enzymes in human cells. Our data suggests that OTUD4 functions as a component of a complex with multiple, differentially regulated deubiquitinase activities to control alkylation repair, as well as impacting DNA damage signaling. Together, our work implicates ubiquitination as a critical regulator of alkylation damage repair, an unexplored area which we seek to understand in this proposal. Specifically, we will test the hypothesis that OTUD4 serves as a deubiquitinase complex scaffold that promotes alkylation chemoresistance, both in vitro and in a mouse tumor model (Aim 1). We will also determine how the catalytic specificity of this deubiquitinase may be regulated by post- translational modification to modulate DNA damage response signaling (Aim 2). Finally, we will test the hypothesis that non-proteasomal ubiquitination plays a role in the activation of the ALKBH3 pathway (Aim 3). Beyond its implications on our understanding of DNA repair pathways, this work will provide new insights into tumor responses to alkylation chemotherapy, and may reveal novel small molecule targets for chemo sensitization.

Public Health Relevance

The research proposed in this grant has significance for the way in which cells guard their genomes, a pathway important for cancer development as well as cancer treatment. The proposed studies will shed light on the molecular mechanisms in this pathway, and may lead to novel diagnostic and therapeutic avenues in cancer.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA193318-02
Application #
9032479
Study Section
Cancer Etiology Study Section (CE)
Program Officer
Okano, Paul
Project Start
2015-04-01
Project End
2020-03-31
Budget Start
2016-04-01
Budget End
2017-03-31
Support Year
2
Fiscal Year
2016
Total Cost
Indirect Cost
Name
Washington University
Department
Pathology
Type
Schools of Medicine
DUNS #
068552207
City
Saint Louis
State
MO
Country
United States
Zip Code
63130
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Hung, Putzer J; Johnson, Britney; Chen, Bo-Ruei et al. (2018) MRI Is a DNA Damage Response Adaptor during Classical Non-homologous End Joining. Mol Cell 71:332-342.e8
Soll, Jennifer M; Brickner, Joshua R; Mudge, Miranda C et al. (2018) RNA ligase-like domain in activating signal cointegrator 1 complex subunit 1 (ASCC1) regulates ASCC complex function during alkylation damage. J Biol Chem 293:13524-13533
Soll, Jennifer M; Sobol, Robert W; Mosammaparast, Nima (2017) Regulation of DNA Alkylation Damage Repair: Lessons and Therapeutic Opportunities. Trends Biochem Sci 42:206-218
Brickner, Joshua R; Soll, Jennifer M; Lombardi, Patrick M et al. (2017) A ubiquitin-dependent signalling axis specific for ALKBH-mediated DNA dealkylation repair. Nature 551:389-393
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Zhao, Yu; Majid, Mona C; Soll, Jennifer M et al. (2015) Noncanonical regulation of alkylation damage resistance by the OTUD4 deubiquitinase. EMBO J 34:1687-703