ARNT PROTEIN, DEVELOPMENT AND CARCINOGENESIS

所有或几乎所有的毒理效应都是由ah受体介导的。 卤代芳香烃(HAHS)，如2，3，7，8- 四氯二苯并对二恶英(TCDD)这些化合物具有肿瘤的作用。 啮齿动物中的启动子。Ah受体也直接参与了 多种引发剂的致癌作用。受体也可能扮演着一个 在胚胎发育中的作用。DNA结合，转录活性 培养的肝细胞中的ah受体的形式是ah的异源二聚体 受体核转位蛋白与配体结合 Ah受体的亚单位。然而，目前还不清楚是否有一些 配体结合亚基和ArnT的活性可以被表现出来 独立于另一种蛋白质。该项目建议使用 转基因小鼠技术解决ARNT的潜在作用 蛋白质在非遗传毒性和遗传毒性致癌物的致癌作用中，以及 在发育过程中。胚性茎中的一个Arnt等位基因 细胞系将被同源重组灭活。目标人群 ES细胞将被用来产生对被破坏的ARNT纯合的小鼠 等位基因。如果它们不能存活，发育异常和缺陷 在纯合子胎儿或新生儿的生殖系统中 决心，以便深入了解Arnt在 发展。如果不缺乏的小鼠发育到足够晚的阶段，我们 将确定它们是否对TCDD的毒性作用具有抵抗力 发展。如果Arnt基因敲除小鼠完全存活，我们将调查 成年小鼠是否对TCDD的急性毒性反应具有抵抗力， 从而验证了其他人提出的假设，即一些有毒影响 TCDD是通过Arnt非依赖性途径产生的。如果阿尔特人- 基因敲除老鼠是完全可行的，我们还将产生衍生品 小鼠染色体LacI/Q基因串联体的纯合性研究 4.LacI/Q基因可以用来定量检测所有细胞的突变。 身体。我们将使用Laci/Q导数来检验假设 TCDD(对细菌无遗传毒性，但对 小鼠肝脏)，增强其自发致突变性或致突变性 鼠标中的启动器费用，如果是，增强功能是否取决于 阿恩特。我们还将确定肝脏和结肠癌致癌物质2- 氨基-3-甲基咪唑并[4，5-f]喹恶啉(IQ)可增加 喂饲该化合物的小鼠的肝脏和结肠突变，无论是共喂 TCDD(因此刺激AH受体活性)影响 致突变性，以及如果观察到TCDD的任何影响，这些是 依靠阿诺特。

The Ah receptor mediates all, or nearly all, of the toxicological effects of halogenated aromatic hydrocarbons (HAHs), such as 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD). These compounds act as tumor promoters in rodents. The Ah receptor is also directly involved in carcinogenesis by many initiating agents. The receptor may also play a role in embryonic development. The DNA-binding, transcriptionally active form of the Ah receptor in cultured liver cells is a heterodimer of the Ah receptor nuclear translocator (Arnt) protein and the ligand-binding subunit of the Ah receptor. However, it is not clear whether some activities of the ligand-binding subunit and of Arnt can be manifested independently of the other protein. This project proposes to use transgenic mouse technology to address the potential role of the Arnt protein in carcinogenesis by non-genotoxic and genotoxic carcinogens, and in developmental processes. One Arnt allele in an embryonal stem (ES) cell line will be inactivated by homologous recombination. The targeted ES cells will be used to generate mice homozygous for the disrupted Arnt allele. If they are inviable, the developmental abnormalities and defects in the reproductive system of homozygous fetuses or newborns will be determined, in order to provide insight into the role of Arnt in development. If Arnt deficient mice develop to a late enough stage, we will determine whether they are resistant to the toxic effects of TCDD on development. If Arnt-knockout mice are fully viable we will investigate whether the adult mice are resistant to acute toxic responses to TCDD, thus testing the hypothesis, proposed by others, that some toxic effects of TCDD are produced via an Arnt-independent pathway. If the Arnt- knockout mice are fully viable we will also generate derivatives which are homozygous for a concatemer of the lacI/q gene located on mouse chromosome 4. The lacI/q gene can be used to quantitate mutations in all cells of the body. We will use the lacI/q derivatives to test the hypothesis that TCDD (which is non-genotoxic in bacteria but a complete carcinogen to mouse liver), enhances spontaneous mutagenesis or mutagenicity of initiators in mouse fee, and if so, whether enhancement is dependent on Arnt. We will also ascertain whether the liver and colon carcinogen, 2- amino-3-methylimidazo[4,5-f]quinoxaline (IQ) increases the frequency of liver and colon mutations in mice fed with the compound, whether cofeeding with TCDD (and therefore stimulation of Ah receptor activity) affects mutagenicity, and if any effects of TCDD are observed, whether these are dependent on Arnt.