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p53-cofactor JMY nucleates actin filaments in cells. Expression of the actin nucleation region of JMY in U2OS cells induces the formation of actin filaments (phalloidin, red).letter p451
The assembly of actin networks is dependent on nucleation-promoting factors. A new study identifies JMY as a protein containing two separate nucleation-promoting activities that shuttles between the nucleus and the cytoplasm and promotes cell migration. These observations indicate that JMY is an important factor controlling actin dynamics in motile cells.
To control cell proliferation, signal transduction needs to regulate the cell-cycle machinery. Recent findings show that Akt — a major kinase that coordinates diverse signalling pathways — phosphorylates Skp2, a subunit of the SCF-Skp2 ubiquitin ligase that targets key cell-cycle regulators. Akt1-dependent phosphorylation activates SCF-Skp2 through multiple mechanisms.
Ubiquitin E3 ligases of the RING and HECT families are distinct not only in their catalytic mechanisms but also in targeting substrates. Now it seems that one heterodimeric complex can target substrates to both types of E3 ligase.
Depletion of Ca2+ from intracellular stores has long been known to signal to and activate plasma membrane 'store-operated' channels. We now learn that store depletion also controls the formation of cyclic AMP (cAMP) through the regulation of adenylyl cyclase (A-Cyclase). These findings substantially broaden the scope and biological significance of Ca2+ store-regulated signalling.
Beclin 1 is an essential mediator of mammalian autophagy that has anti-tumour activity. Beclin 1 associates with Atg14L and Rubicon to regulate autophagosome formation and maturation, respectively.
Skp2 is a known component of the SCF ubiquitin ligase that targets the cell-cycle regulator p27. Akt kinase phosphorylates Skp2 and regulates its stability and cytoplasmic localization.
The kinase DYRK2 regulates the assembly of a ubiquitin ligase complex in a phosphorylation-independent manner, while also phosphorylating the target for the ligase. Thus, ligase assembly and target ubiquitylation appear to be physically linked processes.
Skp2 is a known component of the SCF ubiquitin ligase that ubiquitylates the cell-cycle regulator p27. Akt kinase directly phosphorylates Skp2 and regulates SCF complex assembly and ligase activity, Skp2 cytoplasmic localization and Skp2-dependent regulation of cell proliferation and migration.
Actin filaments in stereocilia on the surface of inner ear sensory hair cells are continually renewed. Myosin IIIa transports the actin-binding/bundling protein espin to stereocilia tips and cooperates with espin in actin filament elongation.
JMY, originally discovered as a binding partner of the p53 co-activator p300, is an actin-nucleating protein, assembling filaments both by activation of the Arp2/3 complex and through an Arp2/3-independent mechanism.
How a transformed cell interacts with normal cells remains unclear. Most RasV12-transformed cells in an epithelial monolayer are extruded apically in a manner regulated by ROCK, Myosin II and Cdc42, but some cells invade the basal matrix via a mechanism requiring PI3 kinase.
Beclin 1 is an essential mediator of mammalian autophagy that has anti-tumour activity. Two proteins that interact with Beclin 1 have been newly identified and their analysis shows that distinct Beclin 1 complexes regulate autophagosome formation and maturation, respectively.
In yeast, anaphase defects can trigger activation of the NoCut checkpoint, resulting in delayed cytokinesis. The Ilp1/aurora kinase localizes to the spindle midzone and monitors chromatin segregation, thus acting as a chromatin sensor.
During evolution, MAP kinases repeatedly changed substrate specificities and interaction partners. Because of their modular design, they can be experimentally re-designed to achieve rewiring of the signalling network.
STAT3 inhibits glucose production by suppressing the expression of key gluconeogenic genes. In a novel nutrient sensing pathway, the fasting activated longevity protein SirT11 promotes gluconeogenesis by suppressing this inhibitory effect of STAT3.
Depletion of ribosomal protein S6 leads to upregulation of p53 and cell cycle arrest. Surprisingly, p53 induction is not due to nucleolar disruption and Mdm2 inhibition, but rather the selective translation of a class of mRNAs including ribosomal protein L11.