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The Polycomb group protein EZH2 promotes trimethylation of histone H3K27 and gene silencing. Cdk1 and Cdk2 are found to phosphorylate EZH2 and to positively regulate EZH2-mediated effects on global gene silencing, proliferation and migration.
Low oxygen levels are observed in the niche of some stem cells. The hypoxic transcription factor HIF-1 directly regulates Wnt signalling to ensure stem cells maintenance in these niches.
The Prdm16 transcription factor is expressed preferentially in stem cells of the nervous- and the haematopoietic-system and is required for their maintenance. Prdm16 is shown to regulate reactive oxygen species (ROS) levels in the nervous system through an effect on the hepatocyte growth Factor (HGF) promoter.
Quiescent cells contain high levels of both the cell cycle inhibitor p27, and the miRNAs that should negatively regulate it. In response to growth factor, the RNA-binding protein PUM1 interacts with the 3′UTR of p27 to induce a structural change leading to miRNA-mediated downregulation of p27.
A cell-free system has been developed to image vesicle budding and fission events. This method reveals an important role for the F-BAR protein FBP17 in regulating tubulation and clathrin-dependent budding.
How acentrosomal meiotic spindles separate chromosomes in anaphase has been unclear. Although kinetochores are required for the bi-orientation of chromosomes, chromosome separation may instead be driven by CLASP/CLS-2 mediated microtubule assembly.
An RNAi screen of protein phosphatases identifies PP2A–B55α as the main mitotic exit phosphatase in human cells. After mitosis, PP2A–B55α depletion delays the reassembly of the nuclear envelope and Golgi and the decondensation of chromatin.
Little is known about the ultrastructure of focal adhesions, compared with their extensive molecular characterization. Cryo-electron tomography provides novel insights into the internal sub-structures at the interface between adhesions and the actin cytoskeleton.
In bacteria, chromosomes are partitioned by the Par system. Super-resolution microscopy demonstrates that ParA and ParB forms a 'spindle-like' structure and suggests that the pole protein, TipN, anchors the DNA-bound ParA filaments at the new pole.
During yeast cell division, multidrug resistance (MDR) transporters partition unequally, with the older pool remaining in the mother cell. Mutations in MDR transporter genes reduce replicative lifespan, whereas an extra copy of these genes extends it, suggesting that defective MDR proteins may influence replicative ageing.
Tissue-specific stem cells are maintained through signals from their niche. In Drosophila testis, niche-mediated STAT1/2 signals regulate germline stem cells adhesion to their niche, whereas somatic stem cells govern their self-renewal through BMP signalling.
How cell shape influences cell fate decisions is unclear. Epidermal stem cell fate is regulated by cell shape through the actin cytoskeleton and SRF transcriptional activity.
POGZ is identified as a binding partner for HP1 (Heterochomatin Protein 1) and as a regulator of mitotic progression. It mediates the activation of Aurora B and the dissociation of both HP1 and Aurora B from chromosome arms during mitosis.
Different myosin II isoforms have distinct roles at adherens junctions: myosin IIa and IIb localization to junctions is regulated by unique upstream signals and they control specific aspects of junction adhesion and linkage to the actin cytoskeleton.
How factors are targeted to cilia remains largely unknown. A ciliary localization signal targets the KIF17 motor, important for intraflagellar transport, to cilia through importin-β2 and RanGTP.
In humans, immune cell transmigration requires the Rap1 GTPase. A new model of transmigration is characterized in Drosophila, where haemocytes require the GTPase RhoL to trigger Rap1 localization to the leading edge and cell invasion.
The microtubule plus end protein CLIP-170 has been shown to be an AMP activated protein kinase (AMPK) substrate. AMPK-mediated phosphorylation of CLIP-170 regulates microtubule polarization and directional cell migration.
A photoactivatable Rac construct reveals that localized Rac activation in one Drosophila border cell is sufficient to induce protrusion in that cell, with concomitant JNK-dependent retraction in neighbouring cells.
Fisher and colleagues find that Jarid2 is a subunit of PRC2 (Polycomb Repressor Complex 2) that recruits PRC1 complex and Ser 5-phosphorylated RNA Polymerase II to developmental regulators in embryonic stem (ES) cells. Jarid2-deficient ES cells do not efficiently differentiate to mesoderm or neural lineages in vitro.