118 research outputs found

    Nuclear actin extends, with no contraction in sight

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    Within the past two years, actin has been implicated in eukaryotic gene transcription by all three classes of RNA polymerase. Moreover, within just the past year, actin has been identified as a constituent of filaments attached to the nuclear pore complexes and extending into the nucleus. This review summarizes these and other very recent advances in the nuclear actin field and emphasizes the key present issues. On the one hand, we are confronted with a body of evidence for a role of actin in gene transcription but with no known structural basis; on the other hand, there is now evidence for polymeric actin--not likely in the classical F-actin conformation--in the nuclear periphery with no known function. In addition, numerous proteins that interact with either G- or F-actin are increasingly being detected in the nucleus, suggesting that both monomeric and oligomeric or polymeric forms of actin are at play and raising the possibility that the equilibrium between them, perhaps differentially regulated at various intranuclear sites, may be a major determinant of nuclear function

    The highly conserved nuclear lamin Ig-fold binds to PCNA: its role in DNA replication

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    This study provides insights into the role of nuclear lamins in DNA replication. Our data demonstrate that the Ig-fold motif located in the lamin C terminus binds directly to proliferating cell nuclear antigen (PCNA), the processivity factor necessary for the chain elongation phase of DNA replication. We find that the introduction of a mutation in the Ig-fold, which alters its structure and causes human muscular dystrophy, inhibits PCNA binding. Studies of nuclear assembly and DNA replication show that lamins, PCNA, and chromatin are closely associated in situ. Exposure of replicating nuclei to an excess of the lamin domain containing the Ig-fold inhibits DNA replication in a concentration-dependent fashion. This inhibitory effect is significantly diminished in nuclei exposed to the same domain bearing the Ig-fold mutation. Using the crystal structures of the lamin Ig-fold and PCNA, molecular docking simulations suggest probable interaction sites. These findings also provide insights into the mechanisms underlying the numerous disease-causing mutations located within the lamin Ig-fold

    Impact of Engineered Nanomaterials on Health: Considerations for Benefit-Risk Assessment

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    Nanotechnology encompasses the design, characterisation, production and application of materials and systems by controlling shape and size at the nanoscale (nanometres). Nanomaterials may differ from other materials because of their relatively large specific surface area, such that surface properties become particularly important. There has been rapid growth in investment in nanotechnology by both the public and private sectors worldwide. In the EU, nanotechnology is expected to become an important strategic contributor to achieving economic gain and societal and individual benefits. At the same time there is continuing scientific uncertainty and controversy about the safety of nanomaterials. It is important to ensure that timely policy development takes this into consideration. Uncertainty about safety may lead to polarised public debate and to business unwillingness to invest further. A clear regulatory framework to address potential health and environmental impacts, within the wider context of evaluating and communicating the benefit-risk balance, must be a core part of Europe's integrated efforts for nanotechnology innovation. While a number of studies have been carried out on the effect of environmental nanoparticles, e.g. from combustion processes, on human health, there is yet no generally acceptable paradigm for safety assessment of nanomaterials in consumer and other products. Therefore, a working group was established to consider issues for the possible impact of nanomaterials on human health focussing specifically on engineered nanomaterials. This represents the first joint initiative between EASAC and the Joint Research Centre of the European Commission. The working group was given the remit to describe the state of the art of benefits and potential risks, current methods for safety assessment, and to evaluate their relevance, identify knowledge gaps in studying the safety of current nanomaterials, and recommend on priorities for nanomaterial research and the regulatory framework. This report focuses on key principles and issues, cross-referencing other sources for detailed information, rather than attempting a comprehensive account of the science. The focus is on human health although environmental effects are also discussed when directly relevant to healt

    The biodistribution of self-assembling protein nanoparticles shows they are promising vaccine platforms

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    Background Because of the need to limit side-effects, nanoparticles are increasingly being studied as drug-carrying and targeting tools. We have previously reported on a scheme to produce protein-based self-assembling nanoparticles that can act as antigen display platforms. Here we attempted to use the same system for cancer-targeting, making use of a C-terminal bombesin peptide that has high affinity for a receptor known to be overexpressed in certain tumors, as well as an N-terminal polyhistidine tag that can be used for radiolabeling with technetium tricarbonyl. Results In order to increase circulation time, we experimented with PEGylated and unPEGylated varities typo particle. We also tested the effect of incorporating different numbers of bombesins per nanoparticle. Biophysical characterization determined that all configurations assemble into regular particles with relatively monodisperse size distributions, having peaks of about 33 – 36 nm. The carbonyl method used for labeling produced approximately 80% labeled nanoparticles. In vitro, the nanoparticles showed high binding, both specific and non-specific, to PC-3 prostate cancer cells. In vivo, high uptake was observed for all nanoparticle types in the spleens of CD-1 nu/nu mice, decreasing significantly over the course of 24 hours. High uptake was also observed in the liver, while only low uptake was seen in both the pancreas and a tumor xenograft. Conclusions The data suggest that the nanoparticles are non-specifically taken up by the reticuloendothelial system. Low uptake in the pancreas and tumor indicate that there is little or no specific targeting. PEGylation or increasing the amount of bombesins per nanoparticle did not significantly improve targeting. In particular, the uptake in the spleen, which is a primary organ of the immune system, highlights the potential of the nanoparticles as vaccine carriers. Also, the decrease in liver and spleen radioactivity with time implies that the nanoparticles are broken down and cleared. This is an important finding, as it shows that the nanoparticles can be safely used as a vaccine platform without the risk of prolonged side effects. Furthermore, it demonstrates that technetium carbonyl radiolabeling of our protein-based nanoparticles can be used to evaluate their pharmacokinetic properties in vivo.ISSN:1477-315