Date of Award


Document Type


Degree Name

Master of Science (MS)


School of Biological Sciences

First Advisor

Erik Larson


Guanine-rich segments of genomes promote the formation of a four-stranded DNA structure called G-quadruplex (G4 DNA). While evolutionarily conserved, guanine repeats show increased rates of mutagenesis and instability, and this is likely associated with G4 formation. In this thesis, I sought to clarify the molecular sources of genetic instability by testing the repair, excision, and synthesis through guanine-rich DNA. Using E. coli UDG and human SMUG1, I found that uracil is inefficiently repaired in proximity to G4 DNA in vitro. Investigation of E. coli exonuclease III and exonuclease I activity indicated that G4 DNA is a block to activity and complete DNA digestion. Finally, I studied the role of the Y-family translesion polymerase DPO4 in G4 DNA replication bypass. Consistent with known translesion synthesis activities, experiments using Y-family translesion polymerase DPO4 showed an increased fidelity across from structured DNA compared to single-stranded templates. Together these data indicate a possible source of increased mutagenesis around G4 DNA, suggesting that lower levels of DNA repair may promote base substitutions within guanine repeats. In order to limit replication stalling at G4 DNA, the Y-family translesion polymerases may be critical for ensuring faithful replication through DNA repeats and loss of such activities would increase the potential for recombination and genome instability at repetitive loci.


Imported from ProQuest Alvarado_ilstu_0092N_11086.pdf


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