DNA Secondary Structures in the Promoters of Human VEGF and RET Genes and Their Roles in Gene Transcriptional Regulation

Persistent Link:
http://hdl.handle.net/10150/195943
Title:
DNA Secondary Structures in the Promoters of Human VEGF and RET Genes and Their Roles in Gene Transcriptional Regulation
Author:
Guo, Kexiao
Issue Date:
2008
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Unusual DNA secondary structures, especially G-quadruplexes and i-motifs, play important roles in gene transcriptional regulation and have been identified as novel drug targets. In this dissertation, I explored their formation in the human VEGF and RET promoters and their roles in gene transcriptional regulation. VEGF is a key regulator of angiogenesis and is up-regulated in many types of tumors. A poly-guanine/poly-cytosine (polyG/polyC) tract in its proximal promoter (-85 to -50 base pairs relative to the transcription starting site) is essential for both basal and inducible VEGF expression. I demonstrated that the guanine-rich (G-rich) and cytosine-rich (C-rich) strands in the VEGF proximal promoter are able to form G-quadruplex and i-motif structures, respectively. The major G-quadruplex formed by the VEGF G-rich sequence is an intramolecular parallel G-quadruplex containing three G-tetrads and a 1:4:1 arrangement of three double-chain-reversal loops (two single-base loops and one loop with four bases). The complementary C-rich sequence in the same region forms an intramolecular i-motif containing six semiprotonated cytosine-cytosine⁺ base pairs and a 2:3:2 loop configuration (two double-base loops and one loop with three bases). The Gquadruplexes formed by the native VEGF G-rich and its derivative sequences were also confirmed by NMR. In addition, various transcription factors including Sp1, hnRNP K, CNBP and nucleolin, which recognize different DNA structural elements including single-stranded, double-stranded or G-quadruplex/i-motif DNA in the VEGF proximal promoter, have been confirmed by EMSA, siRNA and chromatin immunoprecipitation (ChIP) assay, suggesting that the DNA in the VEGF proximal promoter region is capable of undergoing transitions between those three structures. Based on my studies, I have proposed a model to describe how various transcription factors recognize different DNA structures in the VEGF proximal promoter to regulate transcription. In the proximal promoter of another important oncogene RET, I demonstrated that the guanine-rich strand forms an intramolecular parallel G-quadruplex containing three G-tetrads and a 1:3:1 arrangement of three double-chain-reversal loops. The complementary cytosine-rich strand forms an i-motif structure containing six semiprotonated cytosine-cytosine⁺ base pairs and a 2:3:2 loop configuration. Moreover, G-quadruplex-interactive compounds TMPyP4 and telomestatin were shown to further stabilize the RET G-quadruplex structure.
Type:
text; Electronic Dissertation
Keywords:
DNA secondary structures; Drug targeting; Promoter; RET; transcription factors; VEGF
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Biochemistry; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Hurley, Laurence H.
Committee Chair:
Hurley, Laurence H.

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleDNA Secondary Structures in the Promoters of Human VEGF and RET Genes and Their Roles in Gene Transcriptional Regulationen_US
dc.creatorGuo, Kexiaoen_US
dc.contributor.authorGuo, Kexiaoen_US
dc.date.issued2008en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractUnusual DNA secondary structures, especially G-quadruplexes and i-motifs, play important roles in gene transcriptional regulation and have been identified as novel drug targets. In this dissertation, I explored their formation in the human VEGF and RET promoters and their roles in gene transcriptional regulation. VEGF is a key regulator of angiogenesis and is up-regulated in many types of tumors. A poly-guanine/poly-cytosine (polyG/polyC) tract in its proximal promoter (-85 to -50 base pairs relative to the transcription starting site) is essential for both basal and inducible VEGF expression. I demonstrated that the guanine-rich (G-rich) and cytosine-rich (C-rich) strands in the VEGF proximal promoter are able to form G-quadruplex and i-motif structures, respectively. The major G-quadruplex formed by the VEGF G-rich sequence is an intramolecular parallel G-quadruplex containing three G-tetrads and a 1:4:1 arrangement of three double-chain-reversal loops (two single-base loops and one loop with four bases). The complementary C-rich sequence in the same region forms an intramolecular i-motif containing six semiprotonated cytosine-cytosine⁺ base pairs and a 2:3:2 loop configuration (two double-base loops and one loop with three bases). The Gquadruplexes formed by the native VEGF G-rich and its derivative sequences were also confirmed by NMR. In addition, various transcription factors including Sp1, hnRNP K, CNBP and nucleolin, which recognize different DNA structural elements including single-stranded, double-stranded or G-quadruplex/i-motif DNA in the VEGF proximal promoter, have been confirmed by EMSA, siRNA and chromatin immunoprecipitation (ChIP) assay, suggesting that the DNA in the VEGF proximal promoter region is capable of undergoing transitions between those three structures. Based on my studies, I have proposed a model to describe how various transcription factors recognize different DNA structures in the VEGF proximal promoter to regulate transcription. In the proximal promoter of another important oncogene RET, I demonstrated that the guanine-rich strand forms an intramolecular parallel G-quadruplex containing three G-tetrads and a 1:3:1 arrangement of three double-chain-reversal loops. The complementary cytosine-rich strand forms an i-motif structure containing six semiprotonated cytosine-cytosine⁺ base pairs and a 2:3:2 loop configuration. Moreover, G-quadruplex-interactive compounds TMPyP4 and telomestatin were shown to further stabilize the RET G-quadruplex structure.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectDNA secondary structuresen_US
dc.subjectDrug targetingen_US
dc.subjectPromoteren_US
dc.subjectRETen_US
dc.subjecttranscription factorsen_US
dc.subjectVEGFen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineBiochemistryen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorHurley, Laurence H.en_US
dc.contributor.chairHurley, Laurence H.en_US
dc.contributor.committeememberSun, Daekyuen_US
dc.contributor.committeememberYang, Danzhouen_US
dc.contributor.committeememberMcEvoy, Meganen_US
dc.identifier.proquest10046en_US
dc.identifier.oclc659750467en_US
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