Skeiky Y A, Iatrou K
J Biol Chem. 1987 May 15;262(14):6628-36.
A cloned fragment of Bombyx mori genomic DNA containing a pair of chorion genes was injected into Xenopus laevis oocytes. The RNA transcribed from the injected template was examined by primer extension analysis for the presence of transcripts initiated correctly from the two chorion genes. Using as primers a number of fragments derived from various parts of the injected DNA, we have found that transcription initiation around the cap sites of the chorion genes was considerably more frequent than that at other, seemingly random sites of the template. Injection of different quantities of template into the oocytes revealed that at high DNA concentrations, most transcripts were randomly initiated. However, when reduced amounts of DNA were injected into the oocytes, the extent of specific transcription increased dramatically while the proportion of nonspecific transcripts correspondingly decreased. The relative rates of specific initiation from the two chorion genes in injected oocytes resembled closely those observed in choriogenic follicles. Finally, the primer extension analysis revealed the presence of chorion antisense transcripts not only in injected oocytes but also in total RNA derived from follicular cells. The possible origin of these transcripts is discussed.
将含有一对绒毛膜基因的家蚕基因组DNA克隆片段注射到非洲爪蟾卵母细胞中。通过引物延伸分析检测从注射模板转录的RNA，以确定是否存在从两个绒毛膜基因正确起始的转录本。使用从注射DNA的各个部分衍生的多个片段作为引物，我们发现绒毛膜基因帽位点周围的转录起始比模板上其他看似随机的位点要频繁得多。向卵母细胞中注射不同量的模板表明，在高DNA浓度下，大多数转录本是随机起始的。然而，当向卵母细胞中注射较少数量的DNA时，特异性转录的程度显著增加，而非特异性转录本的比例相应降低。注射卵母细胞中两个绒毛膜基因的特异性起始相对速率与在成绒毛膜卵泡中观察到的非常相似。最后，引物延伸分析表明，不仅在注射的卵母细胞中，而且在来自滤泡细胞的总RNA中都存在绒毛膜反义转录本。讨论了这些转录本可能的来源。
