Explore the vast range of titles available.

Background ΔNp63α is an epithelial progenitor cell marker that maintains epidermal stem cell self-renewal capacity. Previous studies revealed that UV-damage induced p53 phosphorylation is confined to ΔNp63α-positive cells in the basal layer of human epithelium. Results We now report that phosphorylation of the p53 tumour suppressor is positively regulated by ΔNp63α in immortalised human keratinocytes. ΔNp63α depletion by RNAi reduces steady-state ATM mRNA and protein levels, and attenuates p53 Serine-15 phosphorylation. Conversely, ectopic expression of ΔNp63α in p63-null tumour cells stimulates ATM transcription and p53 Serine-15 phosphorylation. We show that ATM is a direct ΔNp63α transcriptional target and that the ΔNp63α response element localizes to the ATM promoter CCAAT sequence. Structure-function analysis revealed that the ΔNp63-specific TA2 transactivation domain mediates ATM transcription in coordination with the DNA binding and SAM domains. Conclusions Germline p63 point mutations are associated with a range of ectodermal developmental disorders, and targeted p63 deletion in the skin causes premature ageing. The ΔNp63α-ATM-p53 damage-response pathway may therefore function in epithelial development, carcinogenesis and the ageing processes.

Exceptional progress has been made in the past two decades in mapping oncogenes and tumour suppressors, defining a function for these master switches, and identifying novel anti-cancer drug targets. The p53 tumour suppressor is a central component of a DNA-damage-inducible pathway controlled by the a taxia t elangiectasia m utated (ATM) and CHK2 protein kinases that have a central role in cancer suppression. One limitation of current human cancer research is the difficulty in developing genetic models that reveal the post-translational regulation of a growth suppressor like CHK2 within the microenvironment of a human tumour. Gaining such insights is important since yeast models and human tissue culture cell lines do not necessarily predict how enzymes like CHK2 are regulated in vivo , and therefore what factors can affect CHK2 tumour suppressor function. Translational cancer research aims to link basic research methodologies and clinical biology by uncovering cancer-specific pathways not revealed by other approaches. This approach is exemplified by two studies in this edition of Oncogene : both use a set of well-characterized human cancers with the objective of identifying novel post-translational control of the tumour suppressor CHK2. The authors have revealed two unexpected epigenetic modifications of the CHK2 pathway in vivo : (1) constitutive phosphorylation of CHK2 at its ATM-activated site in the absence of exogenous DNA damage; and (2) the production of hyper-spliced and inactive isoforms of CHK2. These studies highlight the need to develop model systems to understand why CHK2-activating pathways are being triggered or suppressed in different human cancers and whether the splicing machinery can be manipulated to control the activity of CHK2 for therapeutic benefit.

[DELTA]Np63[alpha] is an epithelial progenitor cell marker that maintains epidermal stem cell self-renewal capacity. Previous studies revealed that UV-damage induced p53 phosphorylation is confined to [DELTA]Np63[alpha]-positive cells in the basal layer of human epithelium. We now report that phosphorylation of the p53 tumour suppressor is positively regulated by [DELTA]Np63[alpha] in immortalised human keratinocytes. [DELTA]Np63[alpha] depletion by RNAi reduces steady-state ATM mRNA and protein levels, and attenuates p53 Serine-15 phosphorylation. Conversely, ectopic expression of [DELTA]Np63[alpha] in p63-null tumour cells stimulates ATM transcription and p53 Serine-15 phosphorylation. We show that ATM is a direct [DELTA]Np63[alpha] transcriptional target and that the [DELTA]Np63[alpha] response element localizes to the ATM promoter CCAAT sequence. Structure-function analysis revealed that the [DELTA]Np63-specific TA2 transactivation domain mediates ATM transcription in coordination with the DNA binding and SAM domains. Germline p63 point mutations are associated with a range of ectodermal developmental disorders, and targeted p63 deletion in the skin causes premature ageing. The [DELTA]Np63[alpha]-ATM-p53 damage-response pathway may therefore function in epithelial development, carcinogenesis and the ageing processes.

High level activation of p53-dependent transcription occurs following cellular exposure to genotoxic damaging agents such as UV-C, while ionizing radiation damage does not induce a similarly potent induction of p53-dependent gene expression. Reasoning that one of the major differences between UV-C and ionizing radiation damage is that the latter does not inhibit general transcription, we attempted to reconstitute p53-dependent gene expression in ionizing irradiated cells by co-treatment with selected transcription inhibitors that alone do not activate p53. p53-dependent transcription can be dramatically enhanced by the treatment of ionizing irradiated cells with low doses of DRB, which on its own does not induce p53 activity. The mechanism of ionizing radiation-dependent activation of p53-dependent transcription using DRB is more likely due to inhibition of gene transcription rather than prolonged DNA damage, as the non-genotoxic and general transcription inhibitor Roscovitine also synergistically activates p53 function in ionizing irradiated cells. These results identify two distinct signal transduction pathways that cooperate to fully activate p53-dependent gene expression: one responding to lesions induced by ionizing radiation and the second being a kinase pathway that regulates general RNA Polymerase II activity.

DeltaNp63alpha is an epithelial progenitor cell marker that maintains epidermal stem cell self-renewal capacity. Previous studies revealed that UV-damage induced p53 phosphorylation is confined to DeltaNp63alpha-positive cells in the basal layer of human epithelium. We now report that phosphorylation of the p53 tumour suppressor is positively regulated by DeltaNp63alpha in immortalised human keratinocytes. DeltaNp63alpha depletion by RNAi reduces steady-state ATM mRNA and protein levels, and attenuates p53 Serine-15 phosphorylation. Conversely, ectopic expression of DeltaNp63alpha in p63-null tumour cells stimulates ATM transcription and p53 Serine-15 phosphorylation. We show that ATM is a direct DeltaNp63alpha transcriptional target and that the DeltaNp63alpha response element localizes to the ATM promoter CCAAT sequence. Structure-function analysis revealed that the DeltaNp63-specific TA2 transactivation domain mediates ATM transcription in coordination with the DNA binding and SAM domains. Germline p63 point mutations are associated with a range of ectodermal developmental disorders, and targeted p63 deletion in the skin causes premature ageing. The DeltaNp63alpha-ATM-p53 damage-response pathway may therefore function in epithelial development, carcinogenesis and the ageing processes.

Induction of the transactivation function of p53 after cellular irradiation was studied under conditions in which upstream signaling events modulating p53 activation were uncoupled from those regulating stabilization. This investigation prompted the discovery of a novel radiation-responsive kinase pathway targeting Ser20 that results in the masking of the DO-1 epitope in undamaged cells. Unmasking of the DO-1 epitope via dephosphorylation occurs in response to low doses of non-ionizing radiation. Our data show that phosphorylation at Ser20 reduces binding of the mdm2 protein, suggesting that a function of the Ser20-kinase pathway may be to produce a stable pool of inactive p53 in undamaged cells which can be readily activated after cellular injury. Phospho-specific monoclonal antibodies were used to determine whether the Ser20 signaling pathway is coupled to the Ser15 and Ser392 radiation-responsive kinase pathways. These results demonstrated that: (1) dephosphorylation at Ser20 is co-ordinated with an increased steady-state phosphorylation at Ser392 after irradiation, without p53 protein stabilization, and (2) stabilization of p53 protein can occur without Ser15 phosphorylation at higher doses of radiation. These data show that the Ser20 and Ser392 phosphorylation sites are both targeted by an integrated network of signaling pathways which is acutely sensitive to radiation injury.

The deep sea, the largest ecosystem on Earth and one of the least studied, harbours high biodiversity and provides a wealth of resources. Although humans have used the oceans for millennia, technological developments now allow exploitation of fisheries resources, hydrocarbons and minerals below 2000 m depth. The remoteness of the deep seafloor has promoted the disposal of residues and litter. Ocean acidification and climate change now bring a new dimension of global effects. Thus the challenges facing the deep sea are large and accelerating, providing a new imperative for the science community, industry and national and international organizations to work together to develop successful exploitation management and conservation of the deep-sea ecosystem. This paper provides scientific expert judgement and a semi-quantitative analysis of past, present and future impacts of human-related activities on global deep-sea habitats within three categories: disposal, exploitation and climate change. The analysis is the result of a Census of Marine Life--SYNDEEP workshop (September 2008). A detailed review of known impacts and their effects is provided. The analysis shows how, in recent decades, the most significant anthropogenic activities that affect the deep sea have evolved from mainly disposal (past) to exploitation (present). We predict that from now and into the future, increases in atmospheric CO(2) and facets and consequences of climate change will have the most impact on deep-sea habitats and their fauna. Synergies between different anthropogenic pressures and associated effects are discussed, indicating that most synergies are related to increased atmospheric CO(2) and climate change effects. We identify deep-sea ecosystems we believe are at higher risk from human impacts in the near future: benthic communities on sedimentary upper slopes, cold-water corals, canyon benthic communities and seamount pelagic and benthic communities. We finalise this review with a short discussion on protection and management methods.

High shear stresses are known to trigger destructive bond-scission reactions in polymers. Recent work has shown that the same shear forces can be used to accelerate non-destructive reactions in mechanophores along polymer backbones, and it is demonstrated here that such mechanochemical reactions can be used to strengthen a polymer subjected to otherwise destructive shear forces. Polybutadiene was functionalized with dibromocyclopropane mechanophores, whose mechanical activation generates allylic bromides that are crosslinked in situ by nucleophilic substitution reactions with carboxylates. The crosslinking is activated efficiently by shear forces both in solvated systems and in bulk materials, and the resulting covalent polymer networks possess moduli that are orders-of-magnitude greater than those of the unactivated polymers. These molecular-level responses and their impact on polymer properties have implications for the design of materials that, like biological materials, actively remodel locally as a function of their physical environment. Materials typically break down in response to the repeated mechanical forces that they experience during use. Now, it has been shown that a mechanochemically active polymer can respond to shear forces by forming more bonds than are broken, leading to improved mechanical properties under conditions that would otherwise be destructive.

Localized protein synthesis provides spatiotemporal precision for injury responses and growth decisions at remote positions in nerve axons. Terenzio et al. show that this process is controlled by local translation of preexisting axonal mRNA encoding the master regulator mTOR (see the Perspective by Riccio). mTOR controls both its own synthesis and that of most newly synthesized proteins at axonal injury sites, thereby determining the subsequent survival and growth of the injured neuron. Science , this issue p. 1416 ; see also p. 1331 Axonal localization of mTOR mRNA enables subcellular regulation of local protein synthesis in injured nerves. How is protein synthesis initiated locally in neurons? We found that mTOR (mechanistic target of rapamycin) was activated and then up-regulated in injured axons, owing to local translation of mTOR messenger RNA (mRNA). This mRNA was transported into axons by the cell size–regulating RNA-binding protein nucleolin. Furthermore, mTOR controlled local translation in injured axons. This included regulation of its own translation and that of retrograde injury signaling molecules such as importin β1 and STAT3 (signal transducer and activator of transcription 3). Deletion of the mTOR 3′ untranslated region (3′UTR) in mice reduced mTOR in axons and decreased local translation after nerve injury. Both pharmacological inhibition of mTOR in axons and deletion of the mTOR 3′UTR decreased proprioceptive neuronal survival after nerve injury. Thus, mRNA localization enables spatiotemporal control of mTOR pathways regulating local translation and long-range intracellular signaling.

Nucleosomes containing mutant K27M histones in diffuse intrinsic pediatric gliomas (DIPG) exclude PRC2 binding and recruit BET bromodomain proteins; however, residual PRC2-dependent repression of specific loci, is required for DIPG oncogenesis. These results provide a rationale for targeting these epigenetic regulators in patients. Diffuse intrinsic pontine glioma (DIPG) is a highly aggressive pediatric brainstem tumor characterized by rapid and uniform patient demise 1 . A heterozygous point mutation of histone H3 occurs in more than 80% of these tumors and results in a lysine-to-methionine substitution (H3K27M) 2 , 3 . Expression of this histone mutant is accompanied by a reduction in the levels of polycomb repressive complex 2 (PRC2)-mediated H3K27 trimethylation (H3K27me3), and this is hypothesized to be a driving event of DIPG oncogenesis 4 , 5 . Despite a major loss of H3K27me3, PRC2 activity is still detected in DIPG cells positive for H3K27M 6 , 7 . To investigate the functional roles of H3K27M and PRC2 in DIPG pathogenesis, we profiled the epigenome of H3K27M-mutant DIPG cells and found that H3K27M associates with increased H3K27 acetylation (H3K27ac). In accordance with previous biochemical data 5 , the majority of the heterotypic H3K27M-K27ac nucleosomes colocalize with bromodomain proteins at the loci of actively transcribed genes, whereas PRC2 is excluded from these regions; this suggests that H3K27M does not sequester PRC2 on chromatin. Residual PRC2 activity is required to maintain DIPG proliferative potential, by repressing neuronal differentiation and function. Finally, to examine the therapeutic potential of blocking the recruitment of bromodomain proteins by heterotypic H3K27M-K27ac nucleosomes in DIPG cells, we performed treatments in vivo with BET bromodomain inhibitors and demonstrate that they efficiently inhibit tumor progression, thus identifying this class of compounds as potential therapeutics in DIPG.