Miranda M, Zarivi O, Amicarelli F, Ragnelli A M, Aimola P, Porretta R, Natali P G, Arcadi A, Savino M, Poma A, Bonfigli A
Department of Basic and Applied Biology, University of L'Aquila, Italy.
J Neurooncol. 1997 Jan;31(1-2):185-93. doi: 10.1023/a:1005730724500.
This paper presents evidence that L-tyrosine oxidation products and 5,6-dihydroxyindole, an intermediate of melanin synthesis bind to and modify DNA structure, as tested by extracting cell DNA, using topoisomerase I and denaturation assays. When supercoiled plasmid pCU18 or pBR322 DNAs are treated with 5,6-dihydroxyindole the supercoiled species disappear and are converted to species less mobile in a gel retardation test with respect to relaxed DNA, 5,6-Dihydroxyindole causes an easier acid denaturation of the double helix. The results, that are dose dependent, would point to both intercalation and cross-linking of DNA by 5,6-dihydroxyindole and its oxidation product(s). 3H-L-tyrosine deriving radioactivity, bound to nuclear DNA, is higher at low pH, (5.6) if compared to pH 6.8. The highest radioactivity bound to cell DNA is found during the transition from the amelanotic to the melanotic phenotype in human melanoma cell lines. As a control, the binding of 3H-L-tyrosine radioactivity to human prostate fibroblast DNA was investigated.
本文提供的证据表明，L-酪氨酸氧化产物和黑色素合成中间体5,6-二羟基吲哚可结合并改变DNA结构，这是通过提取细胞DNA、使用拓扑异构酶I和变性分析进行测试的。当超螺旋质粒pCU18或pBR322 DNA用5,6-二羟基吲哚处理时，超螺旋形式消失，并在凝胶阻滞试验中相对于松弛DNA转化为迁移率较低的形式，5,6-二羟基吲哚使双螺旋更容易发生酸变性。这些剂量依赖性的结果表明5,6-二羟基吲哚及其氧化产物对DNA既有嵌入作用又有交联作用。与pH 6.8相比，结合到核DNA上的3H-L-酪氨酸放射性在低pH值（5.6）时更高。在人黑色素瘤细胞系从无黑色素表型转变为有黑色素表型的过程中，发现结合到细胞DNA上的放射性最高。作为对照，研究了3H-L-酪氨酸放射性与人前列腺成纤维细胞DNA的结合情况。
