E-cadherin is a ubiquitous component of lateral membranes in epithelial tissues and is required to form the first lateral membrane domains in development. Here, we identify ankyrin-G as a molecular partner of E-cadherin and demonstrate that ankyrin-G and ␤-2-spectrin are required for accumulation of E-cadherin at the lateral membrane in both epithelial cells and early embryos. Ankyrin-G binds to the cytoplasmic domain of E-cadherin at a conserved site distinct from that of ␤-catenin. Ankyrin-G also recruits ␤-2-spectrin to E-cadherin-␤-catenin complexes, thus providing a direct connection between E-cadherin and the spectrin/actin skeleton. In addition to restricting the membrane mobility of E-cadherin, ankyrin-G and ␤-2-spectrin also are required for exit of E-cadherin from the trans-Golgi network in a microtubule-dependent pathway. Ankyrin-G and ␤-2-spectrin co-localize with E-cadherin in preimplantation mouse embryos. Moreover, knockdown of either ankyrin-G or ␤-2-spectrin in one cell of a two-cell embryo blocks accumulation of E-cadherin at sites of cell-cell contact. E-cadherin thus requires both ankyrin-G and ␤-2-spectrin for its cellular localization in early embryos as well as cultured epithelial cells. We have recently reported that ankyrin-G and ␤-2-spectrin collaborate in biogenesis of the lateral membrane (

Abstract. The NUP1 gene of Saccharomyces cerevisiae encodes one member of a family of nuclear pore complex proteins (nucleoporins) conserved from yeast to vertebrates. We have used mutational analysis to investigate the function of Nuplp. Deletion of either the amino-or carboxy-terminal domain confers a lethal phenotype, but partial truncations at either end affect growth to varying extents. Amino-terminal truncation causes mislocalization and degradation of the mutant protein, suggesting that this domain is required for targeting Nuplp to the nuclear pore complex. Carboxy-terminal mutants are stable but do not have wild-type function, and confer a temperature sensitive phenotype. Both import of nuclear proteins and export of poly(A) RNA are defective at the nonpermissive temperature. In addition, nupl mutant cells become multinucleate at all temperatures, a phenotype suggestive of a defect in nuclear migration. Tubulin staining revealed that the mitotic spindle appears to be oriented randomly with respect to the bud, in spite of the presence of apparently normal cytoplasmic microtubules connecting one spindle pole body to the bud tip. EM analysis showed that the nuclear envelope forms long projections extending into the cytoplasm, which appear to have detached from the bulk of the nucleus. Our results suggest that Nuplp may be required to retain the structural integrity between the nuclear envelope and an underlying nuclear scaffold, and that this connection is required to allow reorientation of the nucleus in response to cytoskeletal forces.