Regulation of Nanog in DNA damage response, development and tumorigenesis

描述(申请人提供)：胚胎干细胞(ESCs)能够无限自我更新，并保持分化为体内所有细胞系的多潜能。由于ESCs经历了强劲的细胞增殖，而DNA损伤发生在正常的细胞增殖过程中，因此对ESCs来说，拥有严格的机制来维持遗传稳定性以防止DNA损伤传递给后代是至关重要的。与这一观点一致的是，胚胎干细胞的自发突变率比体细胞低得多。维持胚胎干细胞遗传稳定性的机制尚不清楚。我推测，去除DNA损伤的ESCs的一个主要机制是诱导其分化为其他类型的细胞，以维持ESCs自我更新池的遗传完整性。最近发现的同源结构域蛋白Nanog作为自我更新的主要调节因子，使我们能够检验这一假说。我们推测，DNA损伤可能会抑制Nanog的表达和活性。为了支持这一观点，我们最近的发现表明，DNA损伤通过抑制Nanog的表达而诱导ESCs的分化。肿瘤抑制因子P53在这一过程中是必需的，并通过直接与其启动子结合来抑制Nanog的表达。我提出了三个目的，以进一步阐明DNA损伤后和ESC分化过程中Nanog的表达和活性的调节，并研究Nanog在癌症中的潜在作用。目的1.阐明P53家族成员依赖下调小鼠和人胚胎干细胞Nanog的生理意义。目的2.DNA损伤后胚胎干细胞通过蛋白质-蛋白质相互作用调节Nanog活性。目的3.研究Nanog在发育、遗传稳定性和肿瘤发生中的作用。这些研究与人类健康直接相关。在这种背景下，对Nanog在肿瘤发生中的潜在作用的研究将有助于开发针对Nanog过度表达的癌症的新疗法，包括生殖细胞肿瘤和乳腺癌。此外，这些研究将阐明维持人类胚胎干细胞遗传稳定性的机制，这对未来的人类细胞/组织替代治疗具有巨大的潜力。

DESCRIPTION (provided by applicant): Embryonic stem cells (ESCs) are capable of unlimited self-renewal and retain the pluripotency to differentiate into all cell lineages in the body. Since ESCs undergo robust cellular proliferation and DNA damage occurs during normal cellular proliferation, it is critical for ESCs to possess stringent mechanisms to maintain genetic stability to prevent the passage of DNA damage to the progeny. Consistent with this notion, the spontaneous mutation rate is much lower in ESCs than in somatic cells. The mechanism to maintain genetic stability in ESCs remains unclear. I hypothesize that one primary mechanism to rid of DNA damaged-ESCs is to induce their differentiation into other cell types in order to maintain the genetic integrity of the self-renewing pool of ESCs. Recent discovery of the homeodomain protein Nanog as the master regulator of self-renewal allows us test this hypothesis. We hypothesized that the expression and activities of Nanog might be suppressed in response to DNA damage. In support of this notion, our recent findings indicate that DNA damage induces the differentiation of ESCs by suppressing the Nanog expression. Tumor suppressor p53 is required for this process and suppresses the expression of Nanog by direct binding to its promoter. I propose three aims to further elucidate the regulation of the expression and activity of Nanog after DNA damage and during ESC differentiation, and to study the potential roles of Nanog in cancers. Aim 1. To elucidate physiological importance of p53 family members-dependent downregulation of Nanog in mouse and human ESCs. Aim 2. Regulation of Nanog activities through protein-protein interaction in ESCs after DNA damage. Aim 3. To study the roles of Nanog in development, genetic stability and tumorigenesis. These studies have direct relevance to human health. In this context, the studies of the potential role of Nanog in tumorigenesis will help to develop new therapy for Nanog-overexpressing cancers, including germ cell tumors and breast carcinomas. In addition, these studies will shed light on mechanism that maintains genetic stability in human ESCs, which have a great potential for future human cell/tissue replacement therapy.