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The Arp2/3 complex has emerged as a key regulator of signal-dependent changes in the actin cytoskeleton. Recent biochemical and structural studies provide a wealth of information about how the assembly is regulated by WASP family members and actin filaments, and raise important new questions about this cellular machine.
The formin family of proteins have been implicated in regulation of cell polarity and cytoskeletal function in fungal and animal cells, but the manner in which they affect these processes has been mysterious. Two new studies report that formins in budding yeast are specifically required for the assembly of bundles of parallel actin filaments known as cables.
Early endosomes are the first sorting station from which endocytosed materials are targeted to various intracellular destinations. Recent work has identified the FYVE-domain protein rabenosyn-5 as a bifunctional effector of the GTPases rab5 and rab4, physically connecting entry and recycling sites on early endosomes.
It has long-been accepted that normal somatic cells have intrinsic mechanisms that limit their proliferative lifespan. Recent work has now challenged this view by demonstrating that extrinsic factors might be determining proliferative potential.