The transcriptional basis of tumor promotion

肿瘤促进的转录基础

• 批准号: 7735731
• 负责人: JOSEPH D LOCKER
• 金额: $ 37.48万
• 依托单位: ALBERT EINSTEIN COLLEGE OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-09-30 至 2014-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7735731
• 关键词: Address; Adenoviruses; Apoptosis; Binding; Binding Sites; Biological; Biological Process; Cell Cycle; Cell Proliferation; Complex; Cyclin D1; Funding; Gene Expression; Genes; Genetic Transcription; Goals; Growth; Hepatocyte; Hormones; Hyperplasia; Individual; Injury; Investigation; Knockout Mice; Lead; Ligands; Liver; Liver Regeneration; Malignant Neoplasms; Mediating; Mediator of activation protein; Messenger RNA; Mitogens; Modeling; Molecular; Molecular Profiling; Mus; Mutate; Natural regeneration; Nuclear Receptors; Nucleic Acid Regulatory Sequences; Partial Hepatectomy; Pathway interactions; Pharmaceutical Preparations; Phase; Process; Proteins; Rattus; Regulation; Regulatory Pathway; Research; Research Personnel; Response Elements; Role; Stimulus; System; Tertiary Protein Structure; Testing; Thyroid Hormones; Transcription Coactivator; Transcription Factor AP-1; Transcriptional Activation; Transcriptional Regulation; Tumor Promoters; Tumor Promotion; Work; activating transcription factor; base; cell growth; cell type; chromatin remodeling; novel; null mutation; public health relevance; rapid growth; reconstitution; research study; response; transcription factor

DESCRIPTION (provided by applicant): We compared four processes that activate cell proliferation in the liver: (1) hyperplasia induced by the tumor promoter, TCPOBOP; (2) antipromotional hyperplasia induced by thyroid hormone; (3) rapid liver regeneration after partial hepatectomy (PH) in the rat; and (4) more protracted regeneration after PH in the mouse. The first phase of the project generated a comprehensive system of microarray expression profiles of all four processes. TCPOBOP is a direct ligand for the nuclear receptor transcription factor, CAR, and rapidly induces liver growth and cell proliferation. The expression profiles showed rapid induction of Gadd45¿, Jun, and Fosl2 mRNA after TCPOBOP treatment; we focused on transcriptional regulation of these three genes, and on Cyclin D1 as their downstream target. A Gadd45¿-null mouse had active proliferation after TCPOBOP treatment, but impaired transcription and liver growth. Molecular studies showed that Gadd45¿ directly binds CAR and acts as a transcriptional coactivator. Thus, rapid induction of Gadd45¿ is anabolic and enables the high rate of transcription needed for rapid growth. However, other investigators have found that Gadd45¿ regulates apoptosis and proliferation. The research proposed in Aim 1 will investigate how Gadd45¿, only 18 kD, can function as a coactivator, by determining its binding partners in the transcription complex, and its effects on progressive chromatin remodeling during transcriptional activation. Other experiments will determine how Gadd45¿ can have so many critical functions, by mutating individual protein domains and testing each for effects on CAR-binding, coactivation, activation, apoptosis, and proliferation. Additional studies will use adenovirus to reconstitute mutated Gadd45¿ in the livers of null mice and test the importance of each separate function in hyperplasia. Aim 2 will address the diverse mechanisms by which CAR, a cis acting transcription factor, activates CAR- responsive regulatory regions of Fosl2. Experiments will also test whether Jun and Fosl2 are responsible for inducing hyperplasia, by studying TCPOBOP treatment in conditional Fosl2- and Jun-null mice, and by using adenovirus to induce liver expression vivo. Preliminary studies showed that Fosl2 and Jun combine to stimulate transcription of Cyclin D1 through a novel upstream regulatory region. Aim 3 will investigate the mechanisms that activate Cyclin D1 transcription and explain context-specific stimulation by Fosl2. Experiments will also determine the alternative pathways by which liver regeneration and T3-induced hyperplasia activate Cyclin D1 transcription. PUBLIC HEALTH RELEVANCE: The normal liver has several kinds of growth responses-some promote cancer while others inhibit promotion. These growth responses are very complex because they activate expression of hundreds of genes. The goals of this project are to define the common and distinctive parts of each response, and working from this comparison, determine a unique pathway of drug-induced proliferation and cancer promotion.

描述（申请人提供）：我们比较了肝脏中激活细胞增殖的四种过程：（1）肿瘤启动子TCPOBOP诱导的增生； (2)甲状腺激素引起的抗促增生； （3）大鼠部分肝切除（PH）后肝脏快速再生； (4) 小鼠PH后再生时间更长。该项目的第一阶段生成了所有四个过程的微阵列表达谱的综合系统。 TCPOBOP 是核受体转录因子 CAR 的直接配体，可快速诱导肝脏生长和细胞增殖。表达谱显示 TCPOBOP 处理后 Gadd45¿、Jun 和 Fosl2 mRNA 快速诱导；我们重点研究这三个基因的转录调控，并以 Cyclin D1 作为其下游靶点。 Gadd45 缺失小鼠在 TCPOBOP 治疗后具有活跃的增殖，但转录和肝脏生长受损。分子研究表明，Gadd45¿ 直接结合 CAR 并充当转录共激活因子。因此，Gadd45的快速诱导是合成代谢的，并且能够实现快速生长所需的高转录率。然而，其他研究人员发现 Gadd45¿ 调节细胞凋亡和增殖。目标 1 中提出的研究将通过确定转录复合物中的结合伙伴，以及其在转录激活过程中对渐进染色质重塑的影响，研究仅 18 kD 的 Gadd45 如何充当共激活子。其他实验将通过突变单个蛋白结构域并测试每个蛋白结构域对 CAR 结合、共激活、激活、凋亡和增殖的影响来确定 Gadd45 如何具有如此多的关键功能。其他研究将使用腺病毒在无效小鼠的肝脏中重建突变的 Gadd45，并测试每个单独功能在增生中的重要性。目标 2 将解决 CAR（一种顺式作用转录因子）激活 Fosl2 的 CAR 响应性调控区域的多种机制。实验还将通过研究条件性 Fosl2 和 Jun 缺失小鼠中的 TCPOBOP 治疗以及使用腺病毒诱导体内肝脏表达来测试 Jun 和 Fosl2 是否负责诱导增生。初步研究表明，Fosl2 和 Jun 结合通过一个新的上游调控区域刺激 Cyclin D1 的转录。目标 3 将研究激活 Cyclin D1 转录的机制并解释 Fosl2 的上下文特异性刺激。实验还将确定肝脏再生和 T3 诱导的增生激活 Cyclin D1 转录的替代途径。公众健康相关性：正常肝脏有多种生长反应——一些会促进癌症，而另一些会抑制癌症的发生。这些生长反应非常复杂，因为它们激活数百个基因的表达。该项目的目标是定义每种反应的共同和独特部分，并通过比较确定药物诱导的增殖和癌症促进的独特途径。