Andres A C, Muellener D B, Ryffel G U
Nucleic Acids Res. 1984 Mar 12;12(5):2283-302. doi: 10.1093/nar/12.5.2283.
We report the fate of different derivatives of the vitellogenin genes after injection into fertilized eggs of Xenopus. We injected a constructed minigene as well as a 5' fragment of the A2 vitellogenin gene. The minigene survives in embryogenesis much better than the 5' A2 fragment and is retained more frequently and at a higher level in frog tissues. The mosaic distribution of the foreign DNA in different frog tissues indicates that no integration occurred before the first cleavage stage. The persisting DNA may be partially integrated but is mostly found in an episome-like form. This unintegrated form is not supercoiled and is rearranged. Methylation of the Hpa II sites prior to injection has no influence on the survival of the injected sequences and the Hpa II sites of the surviving DNA are unmethylated irrespective whether the injected DNA was methylated or not. Whereas the derivatives are transcribed in embryos, they cannot be activated by estrogen in the liver of young frogs.
我们报告了卵黄蛋白原基因的不同衍生物在注射到非洲爪蟾受精卵后所发生的情况。我们注射了一个构建的小基因以及A2卵黄蛋白原基因的5'片段。该小基因在胚胎发育过程中的存活情况比5'A2片段好得多，并且在蛙类组织中更频繁且以更高水平保留。外源DNA在不同蛙类组织中的镶嵌分布表明，在第一次卵裂阶段之前没有发生整合。持续存在的DNA可能部分整合，但大多以类附加体的形式存在。这种未整合的形式不是超螺旋的，并且发生了重排。注射前Hpa II位点的甲基化对注射序列的存活没有影响，并且存活DNA的Hpa II位点未甲基化，无论注射的DNA是否被甲基化。虽然这些衍生物在胚胎中被转录，但它们在幼蛙肝脏中不能被雌激素激活。
