REGULATION OF GENE-EXPRESSION IN THE MOUSE OOCYTE AND EARLY PREIMPLANTATION EMBRYO - DEVELOPMENTAL-CHANGES IN SP1 AND TATA BOX-BINDING PROTEIN, TBP

We previously demonstrated that an Sp1-dependent reporter gene is pref erentially expressed in G(2) of the 1-cell mouse embryo following micr oinjection of the male pronucleus when compared to microinjection of t he female pronucleus (P. T. Ram and R. M. Schultz, 1993, Dev. Biol. 15 6, 552-556). We also noted that expression of the reporter gene is not observed following microinjection of the germinal vesicle of the full y grown oocyte. In the present study, we examined expression of this r eporter gene during oocyte growth, as well as the nuclear concentratio n of two transcription factors, Sp1 and the TATA box-binding protein, TBP, during oocyte growth and the first cell cycle. The extent of repo rter gene expression decreases during oocyte growth and this decrease correlates with the decrease in nuclear concentration of Sp1, as deter mined by confocal immunofluorescent microscopy. In addition, results o f immunoblotting experiments also indicate a similar decrease in the t otal concentration of Sp1 during oocyte growth. The nuclear concentrat ion of TBP also decreases during oocyte growth, as determined by confo cal immunofluorescent microscopy. Following fertilization, the pronucl ear concentration of these two transcription factors increases in a ti me-dependent fashion and the concentration of each is greater in the m ale pronucleus as compared to the female pronucleus. For each pronucle us and for each transcription factor, this increase in nuclear concent ration is inhibited by aphidicolin, which inhibits DNA synthesis. Last , the increase in nuclear concentration of these two proteins observed between the 1-cell and 2-cell stages does not require transcription o r cytokinesis.