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Role of the first round of DNA replication in reprogramming gene expression in the preimplantation mouse embryo

The first round of DNA replication has been proposed to provide a window of opportunity for maternally‐derived transcription factors to gain access to their cognate cis‐binding DNA sequences and thereby reprogram the pattern of gene expression that occurs during the 2‐cell stage. Using high‐resolution, two‐dimensional electrophoresis of metabolically radiolabeled polypeptides, we report the expression of a group of several polypeptides whose synthesis in the 2‐cell embryo is due to transcription (i.e., α‐amanitin‐sensitive) and depends on the first round of DNA replication (i.e., aphidicolin‐sensitive). We also describe the synthesis of another subset of α‐amanitin‐sensitive polypeptides whose expression does not require the first round of DNA replication (i.e., aphidicolin‐insensitive). These results are consistent with the proposed role of the first round of DNA replication in reprogramming the pattern of gene expression. Mol. Reprod. Dev. 47:430–434, 1997. © 1997 Wiley‐Liss, Inc.