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It is unclear whether viral particles can induce membrane curvature. Binding of Simian virus 40 (SV40) to the GM1 ganglioside on host plasma membranes leads to membrane curvature and the formation of invaginations in cells and in giant unilamellar vesicles, an effect required for viral infection.
The Wnt/b-catenin pathway controls proliferation and self-renewal of mouse adult neural stem cells, and the nuclear receptor TLX is shown to activate this pathway by inducing expression of Wnt7. Thus, neural stem cells promote their own self-renewal by secreting signalling molecules that act in an autocrine and paracrine mode.
Exosome biogenesis is poorly understood. The small GTPases Rab27a and Rab27b and their effectors, Slp4 and Slac2b, control exosome secretion at different steps by regulating the peripheral localization, retention and docking of exosomal precursors, the multivesicular endosomes.
The RME1 ATPases are implicated in endocytic recycling. C. elegans RME1 interacts with Amphiphysin to regulate endocytic recycling in vivo and the two proteins cooperate in the generation of cargo carriers in vitro. The interaction is conserved in other eukaryotes.
Let-7 microRNA (miRNA) and its target gene lin-28 regulate pluripotency. A second Let-7 target, lin-41, controls miRNA function in stem cells by regulating the turnover of the miRNA effector Argonaute2 through its ubiquitin ligase activity.
In vivo imaging of mammary carcinoma cells reveals that activation of a TGFβ-induced transcriptional response induces the motility of individual cells, allowing them to spread through the blood stream. In the absence of TGFβ, cells migrate as groups and can only metastasize through the lymphatic system.
Topoisomerase I, together with the splicing factor ASF/SF2, prevents the collapse of replication forks by inhibiting the formation of RNA–DNA hybrids during the transcription of genes localized at replicating forks, and thereby suppresses the genomic instability associated with such hybrids.
Administration of spermidine, a polyamine whose concentration declines during ageing, extends lifespan in yeast, flies, worms and in human immune cells. Spermidine prevents early oxidative stress and necrotic cell death and increases the expression of autophagy genes by inhibiting histone acetyltransferases action on histone H3.
A screen for suppressors of breast to lung metastasis leads to the identification of KLF17 (Krüppel-like transcription factor 17), which is shown to be downregulated in breast cancer biopsies. KLF17 inhibits epithelial–mesenchymal transition and invasion by inhibiting the transcription of the metastasis factor Id1.
The transcriptional regulators that couple keratinocyte proliferation arrest with commitment to differentiation are yet to be identified. C/EBPs are shown to couple mice basal keratinocyte cell-cycle exit with commitment to differentiation through, respectively, E2F repression and DNA binding.
Radial centrosomal microtubules have a role in Golgi positioning. Golgi-derived microtubules organized by CLASP are now shown to be required for the unique ribbon-like morphology of the Golgi by bringing together individual Golgi stacks. Disrupting Golgi-derived microtubules leads to defects in polarized secretion and directional cell-migration.
Corticosteroid release in animals is highly pulsatile. Expression of glucocorticoid receptor-regulated genes is induced in a pulse-like manner and is coupled to hormone release in cultured cells and in vivo. Gene pulsing involves rapid receptor exchange on the promoter and cycling through the chaperone machinery.
Neurite extension requires regulation of microtubule dynamics. aPKC phosphorylates and activates Aurora A, leading to its accumulation at the neurite hillock where Aurora A phosphorylates NDEL1 to induce microtubule extension into neurites.
The SADB kinase is shown to control centrosome duplication by localizing to centrosomes and phosphorylating the centrosomal component g-tubulin on Ser 131. Overexpression of SADB or of a phosphomimetic γ-tubulin mutant results in centrosome amplification.
Pairing centres are specialized regions on worm chromosomes that mediate homologous pairing during meiosis. Sequence motifs that recruit proteins involved in pairing have been identified and they are sufficient for chromosome synapsis and segregation during meiosis.
Non-chromatin associated histones are unstable in budding yeast. Tyrosine phosphorylation of histone H3 followed by subsequent ubiquitylation by the ubiquitin conjugating enzymes Ubc4 and Ubc5 and the ubiquitin ligase Tom1 triggers H3 degradation.
Cell fate decisions mediated by Notch signalling generally involve direct cell–cell contact between adjacent cells. A new Arp2/3-dependent actin structure directs the Notch ligand Delta to microvilli in signal-sending cells during sensory organ development in fly.
Caveolae are plasma membrane invaginations implicated in endocytosis. SDPR is a new component of caveolae that facilitates membrane curvature, caveolae formation and tubulation induced by extracellular ligands such as Shiga toxin B.
The cortical microtubule array in plants orients nascent cellulose fibrils by organizing cellulose synthase complexes in the plasma membrane. Microtubules are now shown to facilitate the delivery of these complexes to the plasma membrane through their depolymerizing ends.
Mir-138, identified in a screen for microRNAs associated with synapses, regulates dendritic spine morphogenesis through APT-1, a depalmitoylation enzyme that modulates the membrane localization of the heterotrimeric G protein alpha subunit.