Identification and characterization of nucleolin as a c-myc G-quadruplex-binding protein

Verónica González, Kexiao Guo, Laurence Hurley, Daekyu Sun

Research output: Contribution to journalArticle

150 Citations (Scopus)

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.

Original languageEnglish (US)
Pages (from-to)23622-23635
Number of pages14
JournalJournal of Biological Chemistry
Volume284
Issue number35
DOIs
StatePublished - Aug 28 2009

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G-Quadruplexes
Carrier Proteins
Proto-Oncogenes
Phosphoproteins
Guanine
HeLa Cells
Colonic Neoplasms
Transcriptional Activation
Neoplasms
Plasmids
Genes
Chemical activation
Cell Proliferation
nucleolin
Breast Neoplasms
Growth
Proteins

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

Cite this

Identification and characterization of nucleolin as a c-myc G-quadruplex-binding protein. / González, Verónica; Guo, Kexiao; Hurley, Laurence; Sun, Daekyu.

In: Journal of Biological Chemistry, Vol. 284, No. 35, 28.08.2009, p. 23622-23635.

Research output: Contribution to journalArticle

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AB - 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.

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