MECHANISMS OF TRANSITION METAL-INDUCED CARCINOGENESIS

过渡金属致癌机制

• 批准号: 6289067
• 负责人: Lucy M Anderson
• 金额: --
• 依托单位: DIVISION OF BASIC SCIENCES - NCI
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6289067
• 关键词: DNA damage; DNA repair; chemical carcinogenesis; chemical related neoplasm /cancer; deoxyguanosine; free radical oxygen; heavy metals; histones; kidney; laboratory rat; liver; metal complex; metalloenzyme; molecular oncology; nickel; oxidation; oxidative stress

Certain transition metals, including nickel, chromium, cadmium, and copper, are carcinogenic to humans and/or animals. Their effects include cancer in the progeny of fathers exposed to welding fumes and other metal dusts. However, mechanisms of the carcinogenic activity of these metals remain obscure. In recent years, we have been testing a hypothesis that one such mechanism would involve metal-mediated oxidative damage to DNA and nuclear proteins. In 1998/99 we continued mechanistic studies of that hypothesis. Our investigations on transition metals interactions with protamine HP2 were directed towards binding of Zn(II) and Ni(II) to its model peptides HP2 1-15, HP2 1-25, HP2 26-40, HP2 37-47, HP2 43-57, and the effects of this binding on association of the peptides with a 20-mer double stranded oligonucleotide. Zn(II) was found to bind to all these peptides and increase their association with the oligonucleotide, although with different strength. Zn(II) binding sites differed from those for Ni(II).Using synthetic model peptides, we continued to investigate Ni(II) interactions with the core histones. The formation of a strong complex at pH 7 and above with the TESHHK motif in the C-terminal tail of histone H2A and hydrolysis of this motif by Ni(II) were confirmed in longer peptides, acetyl-TESHHKAKGK, and a 34-mer peptide (H2A 1-34) modeling the entire tail. The primary complexes lack significant oxidation-mediating activity towards DNA. However, a secondary complex formed between Ni(II) and the SHHKAKGK product of hydrolysis of the primary complexes is redox-active and is capable of enhancing oxidative damage by hydrogen peroxide to plasmid DNA (single strand breaks and base oxidation). Also, this complex is degraded by hydrogen peroxide, especially at its histidine and serine residues. Since the physiological roles of the histone tail include locking interactions with other histones and DNA, the observed truncation of this tail by Ni(II) may affect gene expression. The redox activity of the cut-off product may enhance promutagenic damage to DNA.Another investigation focused on 8-oxo-dGTPases, a class of enzymes preventing incorporation of promutagenic 8-oxo-dGTP into DNA. Our former experiments revealed strong inhibition by Cd(II) and weak inhibition by Ni(II) of the isolated mammalian enzyme. Using our newly developed in vivo assay for 8-oxo-dGTPase we confirmed the inhibition of its activity by Cd(II) in the testes of rats exposed to Cd(II), but not Ni(II). The inhibition was accompanied by a significant increase of the promutagenic 8-oxo-dG lesion in testicular DNA. The epigenetic toxicity of Ni(II) was studied in cultured CHO cells. Ni(II) caused cell cycle arrest at G2/M phase and apoptosis. It did not, however, affect the expression of p53 protein. Using the differential display technique, we found that the exposure of cells to Ni(II) resulted in up-regulation of the H ferritin and hSNF2H genes, and down-regulation of the vimentin gene. All the results indicate that Ni(II) and, perhaps, other carcinogenic metals can act through both genetic and epigenetic mechanisms involving oxidative damage and other chemical mechanisms. In addition, our research provides an experimental basis for collaborative studies on oxidative damage by other carcinogenic insults (see projects ZO1 BC 05301 and ZO1 BC 05302). - 8-oxo-dG, Chemical carcinogenesis, dGTPase, DNA damage, DNA repair, Histones, Metal carcinogenesis, Nickel, Nuclear proteins, Protamines,

某些过渡金属，包括镍、铬、镉和铜，对人类和/或动物具有致癌性。它们的影响包括接触焊接烟雾和其他金属粉尘的父亲的后代患癌症。然而，这些金属的致癌活性机制仍不清楚。近年来，我们一直在测试一个假设，即其中一种机制涉及金属介导的 DNA 和核蛋白氧化损伤。 1998/99 年，我们继续对该假设进行机制研究。我们对过渡金属与鱼精蛋白 HP2 相互作用的研究针对 Zn(II) 和 Ni(II) 与其模型肽 HP2 1-15、HP2 1-25、HP2 26-40、HP2 37-47、HP2 43- 的结合。 57，以及这种结合对肽与 20 聚体双链寡核苷酸缔合的影响。研究发现，Zn(II) 可以与所有这些肽结合，并增强它们与寡核苷酸的结合，尽管强度不同。 Zn(II) 结合位点与 Ni(II) 结合位点不同。使用合成模型肽，我们继续研究 Ni(II) 与核心组蛋白的相互作用。在较长的肽、乙酰基-TESHHKAKGK 和 34- 肽中，在 pH 7 及以上与组蛋白 H2A C 末端尾部的 TESHHK 基序形成强复合物，并通过 Ni(II) 水解该基序。 mer 肽 (H2A 1-34) 模拟整个尾巴。初级复合物对 DNA 缺乏显着的氧化介导活性。然而，Ni(II) 和初级复合物水解的 SHHKAKGK 产物之间形成的次级复合物具有氧化还原活性，能够增强过氧化氢对质粒 DNA 的氧化损伤（单链断裂和碱基氧化）。此外，该复合物会被过氧化氢降解，尤其是其组氨酸和丝氨酸残基。由于组蛋白尾部的生理作用包括与其他组蛋白和 DNA 的锁定相互作用，因此观察到 Ni(II) 对该尾部的截断可能会影响基因表达。截止产物的氧化还原活性可能会增强对 DNA 的促突变损伤。另一项研究集中在 8-oxo-dGTP 酶上，这是一类阻止促突变 8-oxo-dGTP 掺入 DNA 的酶。我们之前的实验表明，Cd(II) 对分离的哺乳动物酶具有强抑制作用，而 Ni(II) 则具有弱抑制作用。使用我们新开发的 8-oxo-dGTPase 体内测定法，我们证实了暴露于 Cd(II) 的大鼠睾丸中的 Cd(II) 对其活性的抑制，但不抑制 Ni(II)。这种抑制伴随着睾丸 DNA 中促突变​​ 8-oxo-dG 损伤的显着增加。在培养的 CHO 细胞中研究了 Ni(II) 的表观遗传毒性。 Ni(II) 导致细胞周期停滞在 G2/M 期并导致细胞凋亡。然而，它并不影响p53蛋白的表达。使用差异显示技术，我们发现细胞暴露于 Ni(II) 会导致 H 铁蛋白和 hSNF2H 基因上调，以及波形蛋白基因下调。所有结果表明，Ni(II) 以及其他致癌金属可能通过涉及氧化损伤和其他化学机制的遗传和表观遗传机制发挥作用。此外，我们的研究为其他致癌损伤引起的氧化损伤的合作研究提供了实验基础（参见项目 ZO1 BC 05301 和 ZO1 BC 05302）。 - 8-oxo-dG、化学致癌作用、dGTP酶、DNA损伤、DNA修复、组蛋白、金属致癌作用、镍、核蛋白、鱼精蛋白、