Fidelity of transcription of Xenopus laevis globin genes injected into Xenopus laevis oocytes and unfertilized eggs.

The Xenopus laevis alpha 1- and beta 1-globin genes were injected into oocytes and unfertilized eggs of X. laevis. In oocytes, the injected globin genes were actively transcribed, but the majority of the transcripts were incorrectly initiated. In unfertilized eggs, the injected genes were 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 22-h period. We suggest that the ability of the egg to selectively transcribe the injected X. laevis globin genes from the correct promoter sites may be related to differences in chromatin structure between the oocyte and the unfertilized egg.