Abstract: 507

BEHAVIOR OF THE 100-kDa PROTEIN, A NOVEL MAMMALIAN SPLICING FACTOR, IN MOUSE PREIMPLANTATION EMBRYOS.

A Nishikimi¹ , J Mukai¹ , N Kioka² , M Yamada¹
Laboratory of Reproductive Physiology, Graduate School of Agriculture, Kyoto Univ, Kyoto, Japan ¹
Laboratory of Biochemistry, Graduate School of Agriculture, Kyoto Univ, Kyoto, Japan ²

Dynamic changes of subcellular distribution of pre-mRNA splicing factors in preimplantation embryos have been reported. Recently, we have cloned a novel 100-kDa protein from HeLa cells with homology (44.7% identical) to yeast pre-mRNA splicing factor, Prp1p/Zer1p, that is essential for mRNA splicing and cell cycle transition. A characteristic motif, tetratrico peptide repeat (TPR) that mediates protein-protein interactions, in Prp1p/Zer1p is highly conserved in the 100-kDa protein. Therefore, the 100-kDa protein may be a mammalian homologue of Prp1p/Zer1p. Here we report the cell cycle dependent changes of subcellular distribution of the 100-kDa protein in mouse preimplantation embryos. Indirect immunofluorescent examination using anti-100-kDa protein antibodies revealed that fluorescence was observed both in the nucleus and the cytoplasm in most blastomeres of 8-cell and morula embryos, but in some of their blastomeres, nuclear distribution was not observed. In 1-cell embryos, the fluorescent intensity in the nucleus varied among the embryos observed. To clarify the timing of the distribution changes, we examined cell-cycle-synclonized 1-cell embryos. The fluorescent intensity both in the nucleus and the cytoplasm of all the embryos at G1 and S phases (30 min and 6 h after pronuclear formation, respectively) was almost the same, whereas at the G2 phases (11 h after pronuclear formation), the intensity in the nucleus of all the embryos was much higher than that in the cytoplasm, indicating that the 100-kDa protein is accumulated in the nucleus during the cell cycle transition from S to G2. The findings suggest that the 100-kDa protein is involved in transcriptional regulation as a pre-mRNA splicing factor in mouse embryos.

    This abstract is being presented on Tuesday, August 3 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.