REQUIREMENT FOR PROTEIN-SYNTHESIS DURING EMBRYONIC GENOME ACTIVATION IN MICE

Embryonic genome activation (EGA) occurs by the 2-cell stage in mouse embryos. To understand the molecular basis of EGA, it is important to determine whether EGA can be supported by maternally inherited factors or if it requires the synthesis of additional transcription factors. We used a quantitative reverse transcription-polymerase chain reaction (RT-PCR) method to test whether protein synthesis is required for the transcriptional activation of six housekeeping genes (U2afbp-rs, Hprt , Pdha1, Prps1, Odc, and Cox7c). Cycloheximide treatment reduced the e xpression of these mRNAs in 2-cell embryos to the same degree as alpha -amanitin treatment. Cycloheximide treatment did not reduce the expres sion of maternally inherited mRNAs, indicating that its effect is spec ific for transcription-dependent gene expression. These results contra st with earlier results reported for the Hsp70 gene. This difference m ay reflect differences in promoter require ments. We conclude that pro tein synthesis is required for the activation of most, if not all, hou sekeeping genes in the mouse embryo, and that the time of EGA may be c ontrolled, in part, by the regulated recruitment of maternal mRNAs enc oding key transcription factors. (C) 1997 Wiley-Liss, Inc.