Mouse Transcription-related Events Before And After Fertilization Research

TATA binding protein (TBP) associated factor 1 (TAF1) is a member of the general transcription machinery.Interference in the function of TAF1 could cause a broad transcriptional defect in early embryonic development. To explore possible roles of TAF1 in embryonic transcriptional silence and zygotic genome activation, we examined the expression of TAF1 in 1-cell mouse embryos using an immunofluorescence assay. No TAF1 was detected in embryos in the first few hours after fertilization. TAF1 appeared in pronuclei 6h post-fertilization and reached a relatively high level before zygotic genome activation. These data showed that besides TBP, another critical member of the general transcription machinery such as TAF1 is also absent or at an extremely low level at the outset of development. Combined deficiency in critical members of the general transcription machinery may account for embryonic transcriptional silence. SRG3 (Smarcc1) is one of the core subunit of the SWI/SNF complex. In the absence of SRG3, embryonic development ceases during peri-implantation stages, indicating that SRG3, as well as the chromatin remodeling process, plays an essential role in early mouse development. To gain a better understanding of chromatin remodeling during the early stages of development, we examined SRG3 expression during oogenesis and pre-implantation stages using immunofluorescence and western blot assays. SRG3 was detected in nuclei of oocytes during growth and maturation. Following fertilization, SRG3 was detected in pronuclei shortly after their formation. Nuclear concentrations of SRG3 increased in a time-dependent fashion and were found to be greater in the male pronucleus than in the female pronucleus. The increase of SRG3 in nuclear could be partially inhibited by a protein synthesis inhibitor but not by a transcriptional inhibitor. Expression of SRG3 is accompanied by expression of Brg1 and Ini1, two other core-subunits of the SWI/SNF complex. The expression of these chromatin remodeling factors parallels with SP1 and TBP spatially and temporally, suggesting that remodeling factors play an important role in chromatin structure and function during early development.