In today's new issue of JCB, Hayakawa et al. reveal that half of all the proteins that form the budding yeast nuclear pore complex are either mono- or poly-ubiquitinated. And they describe in detail how the ubiquitination of one pore component, Nup159, helps recruit dynein to the nuclear envelope in order to orient the spindle and move the nucleus to the bud neck during mitosis. More details here.
Ardite et al. describe how increased production of a microRNA leads to progressive muscle deterioration in Duchenne muscular dystrophy patients. As patients age, their damaged muscle cells are gradually replaced by collagen-rich fibrous tissue. Ardite et al. show that the cytokine TGFbeta induces this muscle fibrosis in part by stimulating production of the microRNA, miR-21, which increases fibroblast proliferation and boosts collagen production. You can read more in this summary.
Tang and Brieher reconstitute the assembly of actin filaments at intercellular junctions in vitro, and use their assay to identify key roles for the Arp2/3 actin nucleation complex and the actin-bundling protein alpha-actinin-4 in the process. These two proteins help assemble actin filaments at the junctions themselves, rather than capturing filaments formed nearby in the cytosol. Moreover, as described in this week's In Focus, the researchers find that versions of alpha-actinin-4 containing a mutation associated with human kidney disease inhibit actin assembly at adherens junctions in vitro and in vivo.
Wynne et al. image the movements of homologous chromosomes in living nematodes in order to describe how they pair up at the beginning of meiosis. These movements rely on chromosome sequences called pairing centers that coupled by a network of proteins across the nuclear envelope to dynein motors and microtubules in the cytoplasm. Dynein is shown to drive rapid, directional movements of the chromosomes to help them pair up with their homologues, but the chromosomes also show slower, dynein-independent motions that help them to pair up even in the absence of the motor protein. More here.
And Arsic et al. reveal a surprising new function for Cyclin A2, a protein best known for regulating cyclin-dependent kinases (CDKs) to control progression through the cell cycle. The researchers show that Cyclin A2 also has a CDK-independent function in inhibiting cell migration by potentiating a guanine nucleotide exchange factor that activates the RhoA GTPase. You can find out more in this month's biobytes podcast, where you can also learn about Giagtzoglou et al.'s paper describing a protein called dEHBP1, which regulates Notch signaling by promoting the exocytosis and recycling of the transmembrane ligand Delta.
There's lots of other interesting papers in today's new issue - you can find them all on our table of contents by clicking here.
Cover image courtesy of David Wynne and Ofer Rog.