The Drosophila Maternal-effect Gene Fs(1)Ya Encodes a Cell Cycle-dependent Nuclear Envelope Component Required for Embryonic Mitosis

The maternal-effect gene fs(1)Ya is specifically required for embryonic mitosis in Drosophila. fs(1)Ya is involved in the initiation of the first embryonic mitosis and may also be necessary for subsequent embryonic mitotic divisions. fs(1)Ya encodes a 91.3 kd hydrophilic protein containing two putative MPF phosphorylation target sites and two potential nuclear localization signals. This protein is synthesized during postoogenic maturation from its maternal RNA and persists throughout embryogenesis. In early embryos, the fs(1)Ya protein is localized to the nuclear envelope from interphase to metaphase. During anaphase and telophase, it is dispersed in the nucleoplasm and cytoplasm, a behavior that is different from that of both the nuclear envelope and lamins. These results suggest that the fs(1)Ya protein is a cell cycle-dependent component of the nuclear envelope that specifically functions in embryonic mitosis.