The Expression of Genes Injected into Oocytes and Eggs of Xenopus Laevis
The Xenopus laevis β1-globin gene was injected into oocytes and unfertilized eggs of X.laevis. In oocytes the injected globin gene was actively transcribed but the majority of the transcripts were incorrectly initiated. Processing of Xenopus globin RNA in oocytes was analyzed using a fusion gene containing the promoter of the Herpes Thymidine Kinase gene and the coding and 3’ non-coding sequences from the β1 globin gene. The transcripts were spliced and polyadenylated at the correct sites with a very high efficiency. In unfertilized eggs the injected gl globin gene was transcribed at a low level but only from the correct start sites. In oocytes the injected circular plasmid DNA containing the cloned globin genes persisted but did not replicate. In contrast, DNA injected into unfertilized eggs replicated up to 15-fold within a 22hr period. Naked DNA injected into either oocytes or eggs is assembled into a chromatin-like structure. The ability of the egg to selectively transcribe the injected Xenopus globin gene from the correct promoter sites may be related to differences in chromatin structure between the oocyte and the unfertilized egg.
KeywordsXenopus Laevis Xenopus Oocyte Globin Gene Herpes Simplex Virus Thymidine Kinase Correct Transcription
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