During prophase in higher cells, centrosomes localize to deep invaginations in the nuclear envelope in a microtubule-dependent process. Loss of nuclear membranes in prometaphase commences in regions of the nuclear envelope that lie outside of these invaginations. Dynein and dynactin complex components concentrate on the nuclear envelope prior to any changes in nuclear envelope organization. These observations suggest a model in which dynein facilitates nuclear envelope breakdown by pulling nuclear membranes and associated proteins poleward along astral microtubules leading to nuclear membrane detachment. Support for this model is provided by the finding that interference with dynein function drastically alters nuclear membrane dynamics in prophase and prometaphase.

Summary Tumor necrosis factor α (TNFα) has both positive and negative roles in human disease. In certain cancers, TNFα is infused locally to promote tumor regression, but dose-limiting inflammatory effects limit broader utility. In autoimmune disease, anti-TNFα antibodies control inflammation in most patients, but these benefits are offset during chronic treatment. TAK1 acts as a key mediator between survival and cell death in TNFα-mediated signaling. Here, we describe Takinib, a potent and selective TAK1 inhibitor that induces apoptosis following TNFα stimulation in cell models of rheumatoid arthritis and metastatic breast cancer. We demonstrate that Takinib is an inhibitor of autophosphorylated TAK1 that binds within the ATP binding pocket, yet is non-competitive, and inhibits by slowing down the rate-limiting step of TAK1 activation. Overall, Takinib is an attractive starting point for the development of inhibitors that sensitize cells to TNFα-induced cell death, with general implications for cancer and autoimmune disease treatment.

The short filaments extending from the cytoplasmic face of nuclear pore complexes are thought to contain docking sites for nuclear import substrates. One component of these filaments is the large O-linked glycoprotein CAN/Nup214. Immunoprecipitation studies carried out under nondenaturing conditions, and using a variety of antibodies, reveal a novel nonglycosylated nucleoporin, Nup84, that is tightly associated with CAN/Nup214. Consistent with such an association, Nup84 is found to be exposed on the cytoplasmic face of the nuclear pore complex. cDNA sequence analyses indicate that Nup84 contains neither the GLFG nor the XFXFG repeats that are a characteristic of a number of other nuclear pore complex proteins. Secondary structure predictions, however, suggest that Nup84 contains a coiled–coil COOH-terminal domain, a conclusion supported by the observation of significant sequence similarity between this region of the molecule and various members of the tropomyosin family. Mutagenesis and expression studies indicate that the putative coiled–coil domain is required for association with the cytoplasmic face of the nuclear pore complex, whereas it is the NH2-terminal region of Nup84 that contains the site of interaction with CAN/Nup214. These findings suggest a model in which Nup84 may function in the attachment of CAN/Nup214 to the central framework of the nuclear pore complex. In this way, Nup84 could play a central role in the organization of the interface between the pore complex and the cytoplasm.