G(2) ARREST AND IMPAIRED NUCLEOCYTOPLASMIC TRANSPORT IN MOUSE EMBRYOSLACKING THE PROTOONCOGENE CAN NUP214/

The vertebrate nucleopore complex (NPC) is a 125 MDa multiprotein asse mbly that mediates nucleocytoplasmic transport, One of its components, CAN/Nup214, is an FXFG repeat-containing protein known to be involved in myeloid leukemia in humans. We have devised a powerful genetic app roach, using maternally derived protein in murine null embryos, to sho w that CAN/Nup214 is essential for NPC function in vivo. We demonstrat e that CAN-/- mouse embryonic stem (ES) cells are not viable and that CAN-/- embryos die in utero between 4.0 and 4.5 days postcoitum, follo wing the depletion of their CAN from maternal sources, In 3.5-day-old mutant embryos, cultured in vitro, progressive depletion of CAN leads to cell cycle arrest in G(2) phase, and eventually to blastocoel colla pse, impaired NLS-mediated protein uptake and nuclear accumulation of polyadenylated RNA, Remarkably, these defective CAN-depleted embryos d o not display any gross morphological abnormalities in their nuclear e nvelopes or NPCs, Our data suggest that CAN is critical to cell cycle progression and required for both nuclear protein import and mRNA expo rt.