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p53 activates Puma-dependent apoptosis and p21-mediated cell-cycle arrest in response to DNA damage. Rudolph and colleagues show that stem-cell functionality in telomerase-deficient mice is improved by the deletion of Puma. Unexpectedly, the accumulation of progenitor cells with damaged short-telomere DNA is not seen in telomerase- and Puma-deficient animals, as p21-mediated cell-cycle arrest is activated to limit the expansion of these cells.
There is a lack of trained scientists to fill the increasing number of jobs and funding opportunities in the Indian scientific research sector. This is a great opportunity for the international scientific community to help build and nurture a vibrant cell biology research community in India.
To establish and maintain their internal organization, living cells must move molecules to their correct locations. Long-range intracellular movements are often driven by motor molecules moving along microtubules, similarly to trucks driving along a highway. Recent work demonstrates that some randomly dispersed cargos can generate actin filaments that form a connected network whose contraction drives collective cargo movement.
The establishment and maintenance of cell polarity requires targeted recruitment of polarity regulators to the plasma membrane. Phosphatidylserine is now shown to have a key role in polarization of yeast cells and the localization of the central polarity regulator Cdc42.
Improperly folded proteins are targeted for destruction through the endoplasmic-reticulum-associated degradation pathway (ERAD). Kopito and colleagues present a high-resolution interaction analysis of the ERAD system in combination with functional genomics, and identify new ERAD components.
Three-colour single-molecule fluorescent in situ hybridization is used by van Oudenaarden and colleagues to show overlapping expression of intestinal stem-cell markers during homeostasis, ageing and regeneration. This approach can help identify putative stem cells in tissues and tumours, and can guide functional studies.
The transcriptional role of c-Myc in maintaining tissue homeostasis is still unclear. Using mice conditionally expressing an activated form of c-Myc in the epidermis, and genome-wide approaches, Frye and colleagues show that c-Myc modulates the expression of the epidermal differentiation complex locus in the skin by displacing or recruiting specific transcriptional regulators. c-Myc activity is negatively regulated in vivo in this context by Sin3a.
In mitotic spindles, each sister chromatid is directly attached to a spindle pole through microtubule bundles known as kinetochore fibres. Microspherule protein 1 (MCRS1) is now shown to support spindle assembly by localizing to the minus ends of kinetochore fibres and protecting them from depolymerization.
Bershadsky and colleagues show that fibroblast polarization depends on matrix rigidity and focal adhesion mechanosensing. They target protein tyrosine kinases through RNAi to identify signalling molecules that regulate traction force generation, focal adhesion assembly and mechanosensitivity.
Chromosomal microtubules participate in formation of kinetochore fibres by attaching their plus ends at kinetochores and focusing their minus ends at the spindle poles. Vernos and colleagues show that the centrosome-localized protein MCRS1 accumulates to chromosomal microtubule minus ends in a RanGTP-dependent manner to prevent microtubule depolymerization and to promote kinetochore-fibre stability and spindle assembly.
Wallerian degeneration occurs in axons following cutting or crush injuries; however, the molecular mechanisms that regulate this process remain elusive. Araki and colleagues find that the ubiquitin ligase ZNRF1 promotes Wallerian degeneration by ubiquitylating AKT, which leads to increased GSK3B activity and subsequent inhibition of the tubulin-binding protein CRMP2.