Role of protein synthesis in the development of a transcriptionally permissive state in one-cell stage mouse embryos

The time of onset of gene transcription in the mouse embryo is temporally r egulated. A prominent feature of this regulation is a change during the one -cell stage from a transcriptionally nonpermissive state to a transcription ally permissive state. During the early one-cell stage, the cytoplasm is ei ther inadequate or suppressive for nuclear gene transcription, but by the l ate one-cell stage, the cytoplasm acquires the ability to support gene tran scription either in endogenous nuclei or exogenous nuclei introduced micros urgically. We have investigated the role of protein synthesis in this cytop lasmic transition. Nuclei from two-cell stage embryos treated with alpha -a manitin were used to evaluate the transcriptional permissiveness of late on e-cell stage cytoplasm, as indicated by the production of transcripts from four genes that are specifically transcribed at elevated rates during the t wo-cell stage. Two of these genes were transcribed following nuclear transf er to late one-cell stage cytoplasm, and two were not transcribed. Treatmen t of the recipient cytoplasm with cycloheximide to inhibit protein synthesi s from the early to the late one-cell stage inhibited the transcription of the two genes that were transcribed in the untreated, late one-cell stage r ecipients. These results indicate that acquisition of the transcriptionally permissive state during the one-cell stage is facilitated by protein synth esis, and that the transcriptional permissiveness in the late one-cell stag e cytoplasm is limited to certain genes.