Mutations occurring spontaneously or induced by exogenous genotoxicants are a root cause of cancer. Nearly all genotoxicant-induced mutations result from DNA damage and replication of the damaged DNA by specialized translesion synthesis (TLS) DNA polymerases that are less accurate than normal replicative DNA polymerases. TLS polymerases are also highly error-prone when copying undamaged DNA, thus constituting a persistent source of genomic instability that needs to be controlled to avoid disease. While the mechanisms of TLS polymerase recruitment to the sites of DNA damage are understood relatively well, the mechanisms that restrict their participation in the normal replication are much less clear. The PI's laboratory has discovered that the participation of DNA polymerase ? (Pol?) in the copying of undamaged DNA is promoted by a variety factors that impede the progression of the replication, including defects in the normal replication machinery, fork stalling at natural impediments and treatment with therapeutic replication inhibitors. This proposal seeks to define the global mechanisms that regulate the extent of error-prone synthesis by Pol? in vivo in DNA damaging and physiological conditions.
In Specific Aim 1, we will determine the role of checkpoint dependent elevation of dNTP pools in shaping the error signature of Pol?.
In Specific Aim 2, we will determine how the contribution of Pol? to DNA synthesis is regulated by the replication dynamics and fork asymmetry. The yeast Saccharomyces cerevisiae model system will be utilized in the studies proposed in Aims 1 and 2, with the goal of using the data obtained in yeast to further advance our understanding of the mechanisms of mutagenesis in human cells.
In Specific Aim 3, we will characterize the mechanism of the mutagenic response to replication defects in human cells. The proposed work will lead to a better understanding of the mutagenic processes that operate in normal cells, as well as those induced by environmental genotoxicants or therapeutic interventions. In the long run, learning to manipulate these processes will help reduce cancer incidence, delay progression and improve therapy outcome.

Public Health Relevance

Gene mutation is a key initiating step in the development of cancer. Pol? plays a major role in the generation of mutations. This proposal seeks to investigate the mechanisms that control the mutagenic activity of Pol?. This research will lead to a better understanding of the events underlying the incidence and progression of cancer, and, in the long run, help develop better preventive and therapeutic approaches.

National Institute of Health (NIH)
National Institute of Environmental Health Sciences (NIEHS)
Research Project (R01)
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Cancer Etiology Study Section (CE)
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Heacock, Michelle
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University of Nebraska Medical Center
Internal Medicine/Medicine
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United States
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Barbari, Stephanie R; Kane, Daniel P; Moore, Elizabeth A et al. (2018) Functional Analysis of Cancer-Associated DNA Polymerase ? Variants in Saccharomyces cerevisiae. G3 (Bethesda) 8:1019-1029
Barbari, Stephanie R; Shcherbakova, Polina V (2017) Replicative DNA polymerase defects in human cancers: Consequences, mechanisms, and implications for therapy. DNA Repair (Amst) 56:16-25
Mertz, T M; Baranovskiy, A G; Wang, J et al. (2017) Nucleotide selectivity defect and mutator phenotype conferred by a colon cancer-associated DNA polymerase ? mutation in human cells. Oncogene 36:4427-4433
Kochenova, Olga V; Bezalel-Buch, Rachel; Tran, Phong et al. (2016) Yeast DNA polymerase ? maintains consistent activity and mutagenicity across a wide range of physiological dNTP concentrations. Nucleic Acids Res :
Mertz, Tony M; Sharma, Sushma; Chabes, Andrei et al. (2015) Colon cancer-associated mutator DNA polymerase ? variant causes expansion of dNTP pools increasing its own infidelity. Proc Natl Acad Sci U S A 112:E2467-76
Kochenova, Olga V; Daee, Danielle L; Mertz, Tony M et al. (2015) DNA polymerase ?-dependent lesion bypass in Saccharomyces cerevisiae is accompanied by error-prone copying of long stretches of adjacent DNA. PLoS Genet 11:e1005110
Northam, Matthew R; Moore, Elizabeth A; Mertz, Tony M et al. (2014) DNA polymerases ? and Rev1 mediate error-prone bypass of non-B DNA structures. Nucleic Acids Res 42:290-306
Kane, Daniel P; Shcherbakova, Polina V (2014) A common cancer-associated DNA polymerase ? mutation causes an exceptionally strong mutator phenotype, indicating fidelity defects distinct from loss of proofreading. Cancer Res 74:1895-901
Kadyrova, Lyudmila Y; Mertz, Tony M; Zhang, Yu et al. (2013) A reversible histone H3 acetylation cooperates with mismatch repair and replicative polymerases in maintaining genome stability. PLoS Genet 9:e1003899
Shah, Kartik A; Shishkin, Alexander A; Voineagu, Irina et al. (2012) Role of DNA polymerases in repeat-mediated genome instability. Cell Rep 2:1088-95

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