archives@tulane.edu / The bulk of nuclear DNA synthesis during replication of the eukaryotic genome is
carried out by three DNA Polymerases (Pols): Pols α, δ and ε. Through its role in leading
strand synthesis, Pol ε is responsible for replicating up to half of the genome. As such,
DNA synthesis errors made Pol ε during replication or other DNA repair processes pose a
considerable source of potential genomic mutagenesis. Pol ε normally displays a high
degree of fidelity, which can be attributed to the action of two physically distinct sites of
catalysis: the polymerase domain, which is responsible for catalyzing the preferential
addition of an incoming deoxynucleoside triphosphate (dNTP) to a nascent DNA strand
resulting in correct Watson-Crick base pairing and the 3’ to 5’ exonuclease domain that
proofreads the nascent DNA strand through the removal of misincorporated bases.
Mutations in either of these domains that adversely affect their function can lead to a
decrease in replication fidelity. Indeed, mutations localized to the exonuclease domain of
Pol ε have been observed in tumors bearing drastically elevated genomic mutation
burdens. We set out to determine the contribution of individual Pol ε mutants to
mutagenesis and mutation spectrum through a combination of in vitro biochemistry and
cell culture. We show that even in the face of functional mismatch repair (MMR) these
mutants can lead to a variable yet substantial level of mutagenesis and recapitulate some
but not all aspects of the anticipated mutation spectrum. These results indicate that Pol ε
exonuclease domain mutants are capable of making these errors but other factors may be
necessary to achieve the entirety of the observed patient tumor mutation profiles. In a
mouse model heterozygous for the most recurrent Pol ε mutant we observe a massive
reduction in tumor-free survival (100% mortality at 10 months) comprise exclusively of
lymphomas. Additionally, the tumor mutation spectrum reveals a significant bias for
TCT>TAT, TCG>TTG and TTT>TGT errors. These data suggest that replication errors
made by Pol ε are directly contributing to tumorigenesis and may be solely responsible
for the Pol ε mutant mutation profile. / 1 / Karl Hodel
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_110739 |
| Date | January 2018 |
| Contributors | Hodel, Karl (author), Pursell, Zachary (Thesis advisor), School of Medicine Biomedical Sciences Graduate Program (Degree granting institution) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | electronic, pages: 194 |
| Rights | No embargo, Copyright is in accordance with U.S. Copyright law. |
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