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The multi-functionality of the adenomatous polyposis coli (APC) tumour suppressor gene keeps surprising cancer molecular biologists. Signal transduction, cytoskeletal organization, chromosomal segregation and cell adhesion are just some of the putative cellular functions previously assigned to this gene and thought to be related to its tumour-suppressing activity. New data on yet another tumour-related function of APC, namely the coordinated regulation of cell adhesion and motility, adds to its host of cellular activities.
Separase is a conserved protease that activates the metaphase-to-anaphase transition by cleaving the link between sister chromatids. Furthermore, in Saccharomyces cerevisiae, separase is also involved in promoting mitotic exit through regulating Cdc14 release. A new study now suggests that the mitotic exit function of separase is independent from its protease activity.
One of the earliest structural changes in cloning by nuclear transfer is the disassembly of the nucleolus. The first insights into the molecular mechanisms of this event have now emerged and the results have tantalising implications for nucleolar architecture.
GTP-binding proteins of the Rho family regulate each other's activities by largely elusive mechanisms. Now, an unexpected signalling pathway has been identified in fibroblasts that links Rac activation to the inhibition of Rho activity, through the release of oxygen radicals.
Signalling pathways involved in axonal growth are the subject of intense study. A new report further highlights the role of the extracellular signal-regulated kinase (ERK)/p35 pathway, but identifies a surprising potential trigger: the death receptor Fas. This study illustrates the importance of cellular context in the functional outcome of a given signalling mechanism.
One of the most fundamental questions of fertilization is how do sperm locate eggs? In many animals and lower plant groups, sperm are guided by chemo-attractants released from eggs. In this issue of Nature Cell Biology, Kaupp and colleagues now examine the very early events of this process in the sea urchin Arbacia punctulata.
In both the nematode Caenorhabditis elegans and mammals, two proteins released from the mitochondrion — apoptosis inducing factor (AIF) and endonuclease G — cooperate in executing programmed cell death. Although both factors can kill cells in a caspase-independent fashion, new studies indicate that their translocation from mitochondria depends, in part, on caspase activation. Together, these data raise new questions about the functional hierarchy between caspases, AIF and mitochondrial membrane permeabilization.