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Confocal microscopy picture showing the influenza A virus nucleoprotein (green), nuclear export protein (blue)and matrixprotein (red, showing as purple when superimposed with blue) trapped in the nucleus of an infected cell treated with the MEK inhibitor U0126. [Cover design: Majo Xeridat] [article, p301]
Recent work in Drosophila has shown that the adherens junctions of epithelial cells provide a planar cue to orientate mitotic spindles during symmetrical division. This planar cue depends on the function of E-APC and dEB1, homologues of the adenomatous polyposis coli (APC) tumour suppressor and of the microtubule-binding yeast protein Bim1.
The identification of proteins that are important for microtubule nucleation, regulation of microtubule dynamics and spindle assembly has been an exciting area of research. A series of recent papers have now provided key insights into these processes by identifying downstream targets of Ran that result in aster formation and spindle assembly.
The universal cell-cycle inhibitor p21Cip1/WAF1 is phosphorylated and localized in the cytoplasm in Her2/neu-overexpressing breast cancers as a result of its physical association with the oncogenic Akt protein. Subcellular mislocalization of checkpoint controllers is now surfacing as a mechanism of deregulating cell proliferation in cancer.
The Arp2/3 complex affects the rate of actin polymerization and promotes cellular actin assembly. Recent work has shown that cortactin is capable of stimulating the actin-nucleating activity of the Arp2/3 complex. In addition, more insight has been gained into how new actin-filament branches are formed and how actin patches in yeast are assembled.