Resistance of DNA G-quadruplex against oxidative stress

The existence of guanine quadruplex (GQ) in the genomic regions with biological significance is closely related to the inhibition of disease progression. Studies have found that GQs at the telomere overhang can inhibit the activity of overly expressed telomerase in the cancer cells. Furthermore, the...

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Main Author: Wee, Xue Xin
Other Authors: Shao Fangwei
Format: Theses and Dissertations
Language:English
Published: 2012
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Online Access:https://hdl.handle.net/10356/50941
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Institution: Nanyang Technological University
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spelling sg-ntu-dr.10356-509412023-02-28T23:31:40Z Resistance of DNA G-quadruplex against oxidative stress Wee, Xue Xin Shao Fangwei School of Physical and Mathematical Sciences DRNTU::Science::Chemistry::Biochemistry The existence of guanine quadruplex (GQ) in the genomic regions with biological significance is closely related to the inhibition of disease progression. Studies have found that GQs at the telomere overhang can inhibit the activity of overly expressed telomerase in the cancer cells. Furthermore, the formation of GQs at promoter regions of oncogenes is capable of regulating the transcription of malignant proteins in the diseased cell lines. The vulnerability of GQs towards oxidative damage is hence interesting to know as the motif concentrates twelve guanines, the genomic oxidation hotspot, into approximately 1 nm3 space. The survivability of the GQs under malignant/physiological ROS levels can be a key towards therapeutic methods against cancer. Furthermore, the rich topological structures distinguish the biological roles of the GQs. Hence, it is of great interests to explore whether and furthermore how the GQ topology would modulate their oxidative resistance. Reactive oxygen/nitrogen species (ROS/RNS) are constantly produced from normal cellular metabolism and inflammatory processes, and are key molecular triggers in cellular signalling pathways. Under pathological conditions such as cancer and cardiovascular diseases etc, oxidative stress, a hike in ROS level, often is presented in cellular compartments. In this thesis work, the oxidative damage in two G-rich genomic sequences, human telomere (HT) and the promoter of cmyc oncogene (cMYC), are interrogated by various ROS threats under both physiological and maligant levels. The resulting DNA damage on guanines and other nucleotides are revealed by alkaline labile strand cleavage and visualized on denature PAGE gel electrophoresis. For both HT and cMYC sequences, comparable guanine damages are observed from both the duplex structures and the GQs under physiological conditions. Folding into GQs does not increase the resistance against the ROS to the genomic DNA under interest comparing to the duplex when the oxidative stress is not stringent. Instead, GQs are found to be more chemically vulnerable under malignant conditions with high ROS levels. Guanine damage and total strand break ups are more pronounced in both GQ under high concentrations of peroxynitrite and hydroxyl radicals. The high vulnerability of GQ towards oxidative stresses suggest a possibility that acceleration of strand breaks in GQ due to oxidative damage may be a key to telomeric shortening and malfunction of oncogenic promoters. The results here may reveal a new biofunction of GQs as a damage hotspot under oxidative threats, and suggests a new anticancer therapeutic strategy as to target GQ for photodynamic therapy MSC(SPMS) 2012-12-24T01:58:19Z 2012-12-24T01:58:19Z 2012 2012 Thesis Wee, X. X. (2012). Resistance of DNA G-quadruplex against oxidative stress. Doctoral thesis, Nanyang Technological University, Singapore. https://hdl.handle.net/10356/50941 10.32657/10356/50941 en 52 p. application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic DRNTU::Science::Chemistry::Biochemistry
spellingShingle DRNTU::Science::Chemistry::Biochemistry
Wee, Xue Xin
Resistance of DNA G-quadruplex against oxidative stress
description The existence of guanine quadruplex (GQ) in the genomic regions with biological significance is closely related to the inhibition of disease progression. Studies have found that GQs at the telomere overhang can inhibit the activity of overly expressed telomerase in the cancer cells. Furthermore, the formation of GQs at promoter regions of oncogenes is capable of regulating the transcription of malignant proteins in the diseased cell lines. The vulnerability of GQs towards oxidative damage is hence interesting to know as the motif concentrates twelve guanines, the genomic oxidation hotspot, into approximately 1 nm3 space. The survivability of the GQs under malignant/physiological ROS levels can be a key towards therapeutic methods against cancer. Furthermore, the rich topological structures distinguish the biological roles of the GQs. Hence, it is of great interests to explore whether and furthermore how the GQ topology would modulate their oxidative resistance. Reactive oxygen/nitrogen species (ROS/RNS) are constantly produced from normal cellular metabolism and inflammatory processes, and are key molecular triggers in cellular signalling pathways. Under pathological conditions such as cancer and cardiovascular diseases etc, oxidative stress, a hike in ROS level, often is presented in cellular compartments. In this thesis work, the oxidative damage in two G-rich genomic sequences, human telomere (HT) and the promoter of cmyc oncogene (cMYC), are interrogated by various ROS threats under both physiological and maligant levels. The resulting DNA damage on guanines and other nucleotides are revealed by alkaline labile strand cleavage and visualized on denature PAGE gel electrophoresis. For both HT and cMYC sequences, comparable guanine damages are observed from both the duplex structures and the GQs under physiological conditions. Folding into GQs does not increase the resistance against the ROS to the genomic DNA under interest comparing to the duplex when the oxidative stress is not stringent. Instead, GQs are found to be more chemically vulnerable under malignant conditions with high ROS levels. Guanine damage and total strand break ups are more pronounced in both GQ under high concentrations of peroxynitrite and hydroxyl radicals. The high vulnerability of GQ towards oxidative stresses suggest a possibility that acceleration of strand breaks in GQ due to oxidative damage may be a key to telomeric shortening and malfunction of oncogenic promoters. The results here may reveal a new biofunction of GQs as a damage hotspot under oxidative threats, and suggests a new anticancer therapeutic strategy as to target GQ for photodynamic therapy
author2 Shao Fangwei
author_facet Shao Fangwei
Wee, Xue Xin
format Theses and Dissertations
author Wee, Xue Xin
author_sort Wee, Xue Xin
title Resistance of DNA G-quadruplex against oxidative stress
title_short Resistance of DNA G-quadruplex against oxidative stress
title_full Resistance of DNA G-quadruplex against oxidative stress
title_fullStr Resistance of DNA G-quadruplex against oxidative stress
title_full_unstemmed Resistance of DNA G-quadruplex against oxidative stress
title_sort resistance of dna g-quadruplex against oxidative stress
publishDate 2012
url https://hdl.handle.net/10356/50941
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