Covalent adducts of DNA and the nonprotein chromophore of neocarzinostatin contain a modified deoxyribose.
Covalent adducts of DNA and the nonprotein chromophore of neocarzinostatin contain a modified deoxyribose.
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DNA 和新制癌菌素非蛋白质发色团的共价加合物含有修饰的脱氧核糖。
DOI：
10.1073/pnas.79.2.369
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发表时间：
1982
影响因子：
11.1
通讯作者：
Goldberg,IH
中科院分区：
文献类型：
--
作者：
Povirk,LF;Goldberg,IH
当新制癌素的非蛋白质发色团被允许与小牛胸腺DNA或poly（dA-dT）反应时。在2-巯基乙醇存在下与聚（dA-dT）反应，并用乙醇沉淀DNA，5%的荧光归因于发色团的萘环与DNA共沉淀。大多数这种荧光通过连续的再沉淀保持附着在DNA上，表明发色团和DNA之间形成共价加合物。酶消化的聚（dA-dT）。聚（dA-dT）-发色团加合物除脱氧腺苷和胸苷外还含有几种可通过反相色谱分离的高荧光疏水产物，所有这些产物均含有腺嘌呤和胸腺嘧啶放射性标记以及发色团放射性标记。一个这样的产品始终有两倍多的胸腺嘧啶腺嘌呤，这表明一个结构发色团-d（TpApT），其中所附的发色团呈现两个磷酸二酯键难对付的核酸内切酶S1。该加合物片段在pH 12下完全水解，释放腺嘌呤、3 '-dTMP和5'-dTMP。在pH 7时，加合物片段以平行动力学缓慢释放发色团和3 '-dTMP，留下修饰的d（ApT），其被蛇毒磷酸二酯酶切割，产生5'-dTMP和修饰的脱氧腺苷。这些水解模式是不同于任何先前表征的碱或磷酸三酯DNA加合物，而是指示改变的脱氧腺苷糖。含有修饰的脱氧核糖的加合物的形成表明脱氧核糖可能是共价生色团附着的位点。这个相同位点的改变，可能是糖部分的5 '-碳，可以解释磷酸二酯键的极端不稳定性。
When the nonprotein chromophore of neocarzinostatin was allowed to react with either calf thymus DNA or poly(dA-dT) . poly(dA-dT) in the presence of 2-mercaptoethanol and the DNA was precipitated with ethanol, 5% of the fluorescence attributable to the naphthalene rings of the chromophore coprecipitated with the DNA. Most of this fluorescence remained attached to DNA through successive reprecipitations, suggesting formation of covalent adducts between chromophore and DNA. Enzymatically digested poly(dA-dT) . poly(dA-dT)-chromophore adduct contained, in addition to deoxyadenosine and thymidine, several highly fluorescent hydrophobic products, separable by reverse-phase chromatography, all of which contained both adenine and thymine radiolabel, as well as chromophore radiolabel. One such product consistently had twice as much thymine as adenine, suggesting a structure chromophore-d(TpApT), in which the attached chromophore rendered both phosphodiester bonds refractory to endonuclease S1. This adduct fragment was completely hydrolyzed at pH 12, releasing adenine, 3'-dTMP, and 5'-dTMP. At pH 7, the adduct fragment slowly released chromophore and 3'-dTMP with parallel kinetics, leaving a modified d(ApT), which was cleaved by snake venom phosphodiesterase to yield 5'-dTMP and a modified deoxyadenosine. These hydrolysis patterns are unlike those of any previously characterized base or phosphotriester DNA adduct but rather indicate an altered deoxyadenosine sugar. The formation of adducts containing a modified deoxyribose suggests that deoxyribose may be the site of covalent chromophore attachment. Alteration of this same site, possibly the 5'-carbon of the sugar moiety, may account for the extreme lability of the phosphodiester bond.