Download The Role of APE1 in DNA Damage Response to Oxidative Stress

The Role of APE1 in DNA Damage Response to
Oxidative Stress
By: Jude Raj
Advisor Dr. Shan Yan
A thesis submitted to the faculty of the University of North Carolina at Charlotte in partial
fulfillment of the requirements for Honors in the Department of Biology
April 2016
Approved by
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Dr. Shan Yan
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Dr. Didier Dreau
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Dr. Christine Richardson
1 Index of Contents
Abstract……………………………………………………………………………………...3
Abbreviation List…………………………………………………………………………...4
Introduction…………………………………………………………………………………5
Materials and Methods…………………………………………………………………….9
Results……………………………………………………………………………………....12
Discussion…………………………………………………………………………………..17
Figures…………………………………………………………………………………….....18
Achievements and Awards ………………………………………………………………..25
Acknowledgements…………………………………………………………………………26
References…………………………………………………………………………………..27
2 Abstract
Cells are continuously being exposed to various insults that can damage the genome of
an organism. The most frequently occurring DNA damage is reactive oxygen species
(ROS)-induced oxidative stress which can lead to the prevention of DNA replication and
transcription. Oxidative stress is shown to cause single-stranded breaks (SSB) in DNA.
However, a built-in response to the oxidative damage takes place called the Base
Excision Repair (BER) pathway that includes crucial enzymes called AP
Endonucleases. One of these enzymes, known as AP Endonuclease 1 (APE1), is a
DNA damage repair enzyme that is known to make a nick in the phosphodiester
backbone of DNA. We show here APE1 plays a previously uncharacterized role in the
DNA Damage Response (DDR), a signaling pathway known to sense, transduce, and
respond to DNA damage. In addition to repairing DNA, we show APE1 is important for
checkpoint signaling due to oxidative stress through its catalytic activity and by directly
interacting with TopBP1 and ATRIP, essential DDR proteins. The domain responsible
for this interaction was found to be APE1’s repair domain. We also show small-molecule
inhibitors of APE1 compromise checkpoint signaling in the presence of oxidative
damage. Therefore, in response to DNA damage by oxidative stress, APE1 responds by
either repairing or recruiting other essential DDR proteins to the damage site. Further
investigations are under way to understand the mechanism behind APE1 and elucidate
its role in both the DDR and BER pathways. Understanding the mechanism behind
APE1 will lead to new methods to use APE1 as a chemopreventive target in cancer.
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