Regulation of Nanog in DNA damage response, development and tumorigenesis

描述（由申请人提供）：胚胎干细胞（ESCs）能够无限自我更新并保持多能性，以分化为体内所有细胞系。由于ESCs具有强大的细胞增殖能力，并且在正常细胞增殖过程中会发生DNA损伤，因此ESCs具有严格的机制来维持遗传稳定性以防止DNA损伤传递给后代至关重要。与这一观点相一致的是，ESCs的自发突变率远低于体细胞。维持ESCs遗传稳定性的机制尚不清楚。我假设去除DNA受损的ESCs的一个主要机制是诱导其分化为其他细胞类型，以维持ESCs自我更新库的遗传完整性。最近发现的同源结构域蛋白Nanog是自我更新的主要调节因子，这使我们能够验证这一假设。我们假设Nanog的表达和活性可能在DNA损伤的反应中受到抑制。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的表达诱导ESCs的分化。这个过程需要肿瘤抑制因子p53，它通过直接结合Nanog的启动子来抑制Nanog的表达。我提出三个目标来进一步阐明Nanog在DNA损伤后和ESC分化过程中的表达和活性调控，并研究Nanog在癌症中的潜在作用。目的1。阐明p53家族成员依赖性的Nanog下调在小鼠和人ESCs中的生理意义。目标2。DNA损伤后ESCs中Nanog活性的蛋白相互作用调控。目标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。在此背景下，研究Nanog在肿瘤发生中的潜在作用将有助于开发针对Nanog过表达癌症的新疗法，包括生殖细胞肿瘤和乳腺癌。此外，这些研究将揭示维持人类ESCs遗传稳定性的机制，这对未来人类细胞/组织替代治疗具有很大的潜力。

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.