Abstract. The Drosophila cell cycle gene fizzy (fzy)is required for normal execution of the metaphaseanaphase transition. We have cloned fzy, and confirmed this by P-element mediated germline transformation rescue. Sequence analysis predicts that fzy encodes a protein of 526 amino acids, the carboxy half of which has significant homology to the Saccharomyces cerevisiae cell cycle gene CDC20. A monoclonal antibody against fzy detects a single protein of the expected size, 59 kD, in embryonic extracts. In early embryos fzy is expressed in all proliferating tissues; in late embryos fzy expression declines in a tissue-specific manner correlated with cessation of cell division. During interphase fzy protein is present in the cytoplasm; while in mitosis fzy becomes ubiquitously distributed throughout the cell except for the area occupied by the chromosomes. The metaphase arrest phenotype caused by fzy mutations is associated with failure to degrade both mitotic cyclins A and B, and an enrichment of spindle microtubules at the expense of astral microtubules. Our data suggest that fzy function is required for normal cell cycleregulated proteolysis that is necessary for successful progress through mitosis.

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The atomic and electronic structure of a tilt grain boundary in rutile TiO 2 has been calculated in an ab initio manner. The method employs a plane-wave basis set and optimized pseudopotentials and is carried out within the local-density approximation of density-functional theory. The study focuses on the structure and energy of the ͚ϭ15 36.9°͑210͓͒001͔ tilt boundary, which is relaxed to equilibrium using a conjugate gradients iterative minimization technique. The calculations confirm the stability of a proposed atomic model for the boundary and provide some insight into its electronic structure. ͓S0163-1829͑96͒08444-5͔

Protein 4.1 functions to link transmembrane proteins with the underlying spectrin/actin cytoskeleton. To permit a genetic analysis of the developmental role and cellular functions of this membrane-skeletal protein, we have identified and characterized its Drosophila homologue (termed D4.1). D4.1 is localized to the septate junctions of epithelial cells and is encoded by the coracle gene, a new locus whose primary mutant phenotype is a failure in dorsal closure. In addition, coracle mutations dominantly suppress Ellipse, a hypermorphic allele of the Drosophila EGF-receptor homologue. These data indicate that D4.1 is associated with the septate junction, and suggest that it may play a role in cell-cell interactions that are essential for normal development.