Identification and Characterization of Nucleolin as a c-myc G-quadruplex-binding Protein
Identification and Characterization of Nucleolin as a c-myc G-quadruplex-binding Protein
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DOI：
10.1074/jbc.m109.018028
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发表时间：
2009-08-28
影响因子：
4.8
通讯作者：
Sun, Daekyu
中科院分区：
文献类型：
--
作者：
Gonzalez, Veronica;Guo, Kexiao;Sun, Daekyu
myc是在促进细胞生长和增殖中起重要作用的原癌基因。了解c-myc的调控在癌症生物学中很重要，因为它在各种人类癌症中过度表达，包括大多数妇科癌症，乳腺癌和结肠癌。我们以前证明，一个鸟嘌呤丰富的区域上游的P1启动子的c-myc，控制85-90%的转录激活该基因可以形成一个分子内的G-四链体（G4），作为一个转录阻遏元件的功能。在这项研究中，我们使用亲和柱来纯化选择性结合人c-myc G-四链体的蛋白质。我们发现，核仁素，多功能磷蛋白，结合在体外的c-myc G-四链体结构具有高亲和力和选择性相比，与其他已知的四链体结构。此外，我们证明，结合后，核仁素有利于形成和增加的c-myc G-四链体结构的稳定性。此外，我们提供的证据表明，核仁素过表达降低了c-myc启动子的活性，大概是通过诱导和稳定的c-myc G-四链体的形成。最后，我们发现核仁素结合到HeLa细胞中的c-myc启动子，这表明这种相互作用发生在体内。总之，核仁素可以诱导体内c-myc G4的形成。
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.