Sun, D., Liu, W., Guo, K., Rusche, J. J., Ebbinghaus, S., Gokhale, V., & Hurley, L. H. (2008). The proximal promoter region of the human vascular endothelial growth factor gene has a G-quadruplex structure that can be targeted by G-quadruplex-interactive agents. Molecular Cancer Therapeutics, 7(4), 880-889.
PMID: 18413801;PMCID: PMC2367258;Abstract:
Previous studies on the functional analysis of the human vascular endothelial growth factor (VEGF) promoter using the full-length VEGF promoter reporter revealed that the proximal 36-bp region (-85 to -50 relative to transcription initiation site) is essential for basal or inducible VEGF promoter activity in several human cancer cells. This region consists of a polypurine (guanine) tract that contains four runs of at least three contiguous guanines separated by one or more bases, thus conforming to a general motif capable of forming an intramolecular G-quadruplex. Here, we show that the G-rich strand in this region is able to form an intramolecular propeller-type parallel-stranded G-quadruplex structure in vitro by using the electrophoretic mobility shift assay, dimethyl sulfate footprinting technique, the DNA polymerase stop assay, circular dichroism spectroscopy, and computer-aided molecular modeling. Two well-known G-quadruplex-interactive agents, TMPyP4and Se2SAP, stabilize G-quadruplex structures formed by this sequence in the presence of a potassium ion, although Se2SAP is at least 10-fold more effective in binding to the G-quadruplex than TMPyP4. Between these two agents, Se2SAP better suppresses VEGF transcription in different cancer cell lines, including HEC1A and MDA-MB-231. Collectively, our results provide evidence that specific G-quadruplex structures can be formed in the VEGF promoter region, and that the transcription of this gene can be controlled by ligand-mediated G-quadruplex stabilization. Our results also provide further support for the idea that G-quadruplex structures may play structural roles in vivo and therefore might provide insight into novel methodologies for rational drug design. Copyright © 2008 American Association for Cancer Research.
Kwok, Y., Sun, D., Clement, J. J., & Hurley, L. H. (1999). The quinobenzoxazines: Relationship between DNA binding and biological activity. Anti-Cancer Drug Design, 14(5), 443-450.
PMID: 10766299;Abstract:
The quinobenzoxazine compounds, derived from antibacterial quinolones, is active in vitro and in vivo against murine and human tumors. In this contribution, we show that the relative DNA binding affinity of the quinobenzoxazine compounds correlates with their cytotoxicity, their ability to inhibit gyrase-DNA complex formation, and the decatenation of kinetoplast DNA by human topoisomerase II. DNA binding studies with the descarboxy-A-62176 analogue indicate that the β-keto acid moiety of the quinobenzoxazine compounds plays an important role in their interaction with DNA.
II, B. M., Seaman, F. C., Wheelhouse, R. T., & Hurley, L. H. (1998). Mechanism for the catalytic activation of ecteinascidin 743 and its subsequent alkylation of guanine N2. Journal of the American Chemical Society, 120(10), 2490-2491.
Hannan, M. A., Estes, R., & Hurley, L. H. (1980). Induction and potentiation of lethal and genetic effects of ultraviolet light by tobacco smoke condensates in yeast. Environmental Research, 21(1), 97-107.
PMID: 6993205;Abstract:
Tobacco smoke condensates (TSC) were tested for DNA repair inhibition in both repair proficient and different classes of repair deficient strains of Saccharomyces cerevisiae. TSC was also tested for induction and potentiation of mutations and mitotic gene conversion in unirradiated and uv-irradiated yeast cells. TSC was found to sensitize all the strains of yeast to uv-inactivation indicating that it acts in a nonspecific manner and does not specifically inhibit a particular repair pathway. Genetic studies showed that TSC, without exogenous metabolic activation, failed to produce mutations while it induced mitotic gene conversion in the diploid strain. At specific concentrations, TSC potentiated both mutagenic and gene convertogenic effects uv-light while at higher concentrations of TSC a reduction of mutations was observed. The results are discussed as they relate to carcinogenesis and cocarcinogenesis/tumor promotion. © 1980.
González, V., Guo, K., Hurley, L., & Sun, D. (2009). Identification and characterization of nucleolin as a c-myc G-quadruplex-binding protein. Journal of Biological Chemistry, 284(35), 23622-23635.
PMID: 19581307;PMCID: PMC2749137;Abstract:
myc is a proto-oncogene that plays an important role in the promotion of cellular growth and proliferation. Understanding the regulation of c-myc is important in cancer biology, as it is overexpressed in a wide variety of human cancers, including most gynecological, breast, and colon cancers. We previously demonstrated that a guanine-rich region upstream of the P1 promoter of c-myc that controls 85-90% of the transcriptional activation of this gene can form an intramolecular G-quadruplex (G4) that functions as a transcriptional repressor element. In this study, we used an affinity column to purify proteins that selectively bind to the human c-myc G-quadruplex. We found that nucleolin, a multifunctional phosphoprotein, binds in vitro to the c-myc G-quadruplex structure with high affinity and selectivity when compared with other known quadruplex structures. In addition, we demonstrate that upon binding, nucleolin facilitates the formation and increases the stability of the c-myc G-quadruplex structure. Furthermore, we provide evidence that nucleolin overexpression reduces the activity of a c-myc promoter in plasmid presumably by inducing and stabilizing the formation of the c-myc G-quadruplex. Finally, we show that nucleolin binds to the c-myc promoter in HeLa cells, which indicates that this interaction occurs in vivo. In summary, nucleolin may induce c-myc G4 formation in vivo. © 2009 by The American Society for Biochemistry and Molecular Biology, Inc.
