TI - Regulation of cap -dependent translation initiation in the early stage porcine parthenotes . AB - The binding of mRNAs to ribosomes is mediated by the protein complex eIF4F in conjunction with eIF4B ( eukaryotic initiation factor 4F and 4B ) . EIF4F is a three subunit complex consisting of eIF4A ( RNA helicase ) , eIF4E (mRNA cap binding protein) , and eIF4G (bridging protein) . The crucial role is played by eIF4E , which directly binds the 5'-cap structure of the mRNA and facilitates the recruitment to the mRNA of other translation factors and the 40S ribosomal subunit . EIF4E binding to mRNA and to other initiation factors is regulated on several levels , including its phosphorylation on Ser-209 , and association with its regulatory protein 4E-binding protein ( 4E-BP1 ) . In this study we document that both the translation initiation factor eIF4E and its regulator 4E-BP1 become dephosphorylated in the early stage porcine zygotes already 8 hr post-activation . Similarly , the activities of ERK1/2 MAP and Mnk1 kinases , which are both involved in eIF4E phosphorylation , gradually decrease during this period with the timing similar to that of eIF4E dephosphorylation . The formation of an active eIF4F complex is also diminished after 9-15 hr post-activation , although substantial amounts of this complex have been detected also 24 hr post-activation ( 2-cell stage ) . The overall protein synthesis in the parthenotes decreases gradually from 12 hr post-activation reaching a minimum after 48 hr ( 4-cell stage ) . Although the translation is gradually decreasing during early preimplantation development , the eIF4F complex , which is temporarily formed , might be a premise for the translation of a small subset of mRNAs at this period of development .