Cytidine deamination to deoxyuridine is a major source of mutation in both the germ-line and cancer cells. Base excision and mismatch repair pathways remove deoxyuridine from double stranded DNA. However, this lesion occurs commonly in single-strand (ss) DNA formed during replication, transcription, and after exposure to DNA damaging agents. Mammalian cells also express the AID/APOBEC family of enzymes that catalyze cytidine deamination in ssDNA and whose aberrant activity has been linked to carcinogenesis. Like the ssDNA they target, expression of APOBEC enzymes is induced by a variety of environmental agents suggesting these exposures may have an important role in carcinogenesis by increasing both APOBEC enzyme and substrate levels. The extent to which APOBEC cytidine deaminases damage nuclear DNA, their potential synergism with environmental DNA damaging agents, and the contribution of deamination-induced mutation to cancer etiology are unknown. Also unclear is how deaminated cytidines are processed within ssDNA. The goal of this proposal is to characterize mechanisms and sources of cytidine deamination-induced mutation and their possible contribution to environmentally-induced cancer.
AIM I will address if the number of APOBEC-induced mutations in human cancers correlates with clinical measures of disease progression and prognosis. The alteration of cancer-related genes by APOBEC-induced mutations will also be determined.
AIM II will determine how conversion of deoxyuridine to abasics sites in ssDNA impacts mutagenesis and ectopic recombination. Deamination-induced mutation and recombination will be measured in yeast lacking damage tolerance mechanisms to access these pathways' roles in mutation and translocation avoidance.
AIM III will address the mutagenic capacity of APOBECs on human chromosomal DNA in a cell line model. The impact environmental exposures that induce ssDNA formation and/or APOBEC expression will be addressed. Whole genome sequencing will be used to identify genome features at risk of APOBEC-mediated mutation.
These aims will provide an understanding of cellular and environmental mechanisms governing cytidine deamination-induced mutation and their contribution to carcinogenesis.

Public Health Relevance

Mutations and chromosome alterations that contribute to cancer progression originate from genetic predispositions as well as exposure environmental agents that damage DNA. This proposal will investigate whether environmental exposures also contribute to genome instability and cancer progression by increasing the potency of cellular enzymes that catalyze a form of mutagenic DNA damage, cytidine deamination.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Research Transition Award (R00)
Project #
5R00ES022633-03
Application #
8989532
Study Section
Special Emphasis Panel (NSS)
Program Officer
Shaughnessy, Daniel
Project Start
2015-01-01
Project End
2017-12-31
Budget Start
2016-01-01
Budget End
2016-12-31
Support Year
3
Fiscal Year
2016
Total Cost
$249,000
Indirect Cost
$78,020
Name
Washington State University
Department
Veterinary Sciences
Type
Schools of Veterinary Medicine
DUNS #
041485301
City
Pullman
State
WA
Country
United States
Zip Code
99164
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Saini, Natalie; Roberts, Steven A; Sterling, Joan F et al. (2017) APOBEC3B cytidine deaminase targets the non-transcribed strand of tRNA genes in yeast. DNA Repair (Amst) 53:4-14
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Mao, Peng; Brown, Alexander J; Malc, Ewa P et al. (2017) Genome-wide maps of alkylation damage, repair, and mutagenesis in yeast reveal mechanisms of mutational heterogeneity. Genome Res 27:1674-1684
Hoopes, James I; Cortez, Luis M; Mertz, Tony M et al. (2016) APOBEC3A and APOBEC3B Preferentially Deaminate the Lagging Strand Template during DNA Replication. Cell Rep 14:1273-1282
Mao, Peng; Smerdon, Michael J; Roberts, Steven A et al. (2016) Chromosomal landscape of UV damage formation and repair at single-nucleotide resolution. Proc Natl Acad Sci U S A 113:9057-62
Saini, Natalie; Roberts, Steven A; Klimczak, Leszek J et al. (2016) The Impact of Environmental and Endogenous Damage on Somatic Mutation Load in Human Skin Fibroblasts. PLoS Genet 12:e1006385
Wyatt, David W; Feng, Wanjuan; Conlin, Michael P et al. (2016) Essential Roles for Polymerase ?-Mediated End Joining in the Repair of Chromosome Breaks. Mol Cell 63:662-673

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