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Guanine nucleotide-exchange factors (GEFs) interact with and activate members of the Rho family of small GTPases through Dbl homology (DH) domains. A new domain has been found in DOCK180 and shown to specifically activate Rho proteins. Interestingly, this module does not contain any homology to Dbl sequences.
Specification of one neurite as the axon is the first milestone achieved as neuronal polarity is established. It is clear that regional changes in the cytoskeleton underlie axonal differentiation, but is one cytoskeletal element any more crucial than the others? Although early studies implicated microtubules, more recent studies have focused on the actin cytoskeleton as the potential hub for factors that influence axonal differentiation. Now, studies on a novel protein called CRMP-2 have shifted attention back to microtubules.
Modulating the cell cycle is essential for viral replication and infection. HIV is an expert at manipulating these processes. New work now shows how apoptosis of CD4/CXCR4-expressing T cells during the course of HIV-infection is intimately connected to aberrant cell-cycle regulation.
Extracellular stimuli transmit information to cells by activating receptor-dependent signal-transduction cascades, most typically involving tyrosine and serine/threonine kinases. The cell's response to the activation of these kinases depends on the duration of their signals. New work now shows how cells sense the duration of an ERK signal in the G1 phase of the cell cycle. The study suggests that a common mechanism for sensing ERK signal duration may be involved in diverse cellular functions.