Activation of the embryonic genome during preimplantation mouse development is characterized by a marked reprogramming of gene expression that is essential for further development. Expression of the protein translation initiation factor eIF-1A gene is driven by a proximal TATA-containing promoter and a distal TATA-less promoter. Using specific amplification of cDNA ends that resolves transcripts derived from the TATA-less and TATA-containing promoters, we find that 70% of the eIF-1A transcripts are derived from the TATA-containing promoter in the fully-grown oocyte. Activation of the embryonic genome during the two-cell stage is accompanied by a change in promoter utilization such that only 25% of the transcripts are now derived from the TATA-containing promoter, i.e., 75% are derived from the TATA-less promoter. When one-cell embryos are cultured to the two-cell stage in the presence of alpha-amanitin, this change in transcript abundance is not observed, i.e., the distribution of transcripts is similar to that observed in the oocyte. By the blastocyst stage only 5% of the transcripts are generated from the TATA-containing promoter. If the change in TATA-box utilization for the eIF-1A reflects an underlying global change in TATA-box utilization, a dramatic change in promoter utilization may occur during preimplantation development such that TATA-less promoters are more efficiently utilized. Such a change in promoter utilization could contribute significantly to the reprogramming of gene expression that occurs during the maternal-to-zygotic transition.
Copyright 2000 Academic Press.