Extracellular signal-regulated kinase 1/2-mediated phosphorylation of p300 enhances myosin heavy chain I/β gene expression via acetylation of nuclear factor of activated T cells c1

The nuclear factor of activated T-cells (NFAT) c1 has been shown to be essential for Ca2+-dependent upregulation of myosin heavy chain (MyHC) I/β expression during skeletal muscle fiber type transformation. Here, we report activation of extracellular signal-regulated kinase (ERK) 1/2 in Ca2+-ionophore-treated C2C12 myotubes and electrostimulated soleus muscle. Activated ERK1/2 enhanced NFATc1-dependent upregulation of a −2.4 kb MyHCI/β promoter construct without affecting subcellular localization of endogenous NFATc1. Instead, ERK1/2-augmented phosphorylation of transcriptional coactivator p300, promoted its recruitment to NFATc1 and increased NFATc1–DNA binding to a NFAT site of the MyHCI/β promoter. In line, inhibition of ERK1/2 signaling abolished the effects of p300. Comparison between wild-type p300 and an acetyltransferase-deficient mutant (p300DY) indicated increased NFATc1–DNA binding as a consequence of p300-mediated acetylation of NFATc1. Activation of the MyHCI/β promoter by p300 depends on two conserved acetylation sites in NFATc1, which affect DNA binding and transcriptional stimulation. NFATc1 acetylation occurred in Ca2+-ionophore treated C2C12 myotubes or electrostimulated soleus. Finally, endogenous MyHCI/β gene expression in C2C12 myotubes was strongly inhibited by p300DY and a mutant deficient in ERK phosphorylation sites. In conclusion, ERK1/2-mediated phosphorylation of p300 is crucial for enhancing NFATc1 transactivation function by acetylation, which is essential for Ca2+-induced MyHCI/β expression

Advances in tissue engineering through stem cell-based co-culture

Stem cells are the future in tissue engineering and regeneration. In a co-culture, stem cells not only provide a target cell source with multipotent differentiation capacity, but can also act as assisting cells that promote tissue homeostasis, metabolism, growth and repair. Their incorporation into co-culture systems seems to be important in the creation of complex tissues or organs. In this review, critical aspects of stem cell use in co-culture systems are discussed. Direct and indirect co-culture methodologies used in tissue engineering are described, along with various characteristics of cellular interactions in these systems. Direct cell–cell contact, cell–extracellular matrix interaction and signalling via soluble factors are presented. The advantages of stem cell co-culture strategies and their applications in tissue engineering and regenerative medicine are portrayed through specific examples for several tissues, including orthopaedic soft tissues, bone, heart, vasculature, lung, kidney, liver and nerve. A concise review of the progress and the lessons learned are provided, with a focus on recent developments and their implications. It is hoped that knowledge developed from one tissue can be translated to other tissues. Finally, we address challenges in tissue engineering and regenerative medicine that can potentially be overcome via employing strategies for stem cel

Southern African guidelines for the safe use of pre-exposure prophylaxis in men who have sex with men who are at risk for HIV infection.

Geneeskunde en GesondheidswetenskappeGeneeskundige VirologiePlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]

Template-free self-assembly of dimeric dicarbocyanine dyes

Symmetrical dicarbocyanine dyes are known to cooperatively assemble on DNA templates. With the goal of developing dyes that are capable of template-free self-assembly, two N-linked dimeric benzothiazole containing pentamethine cyanine dyes have been synthesized. UV-visible spectroscopy of the dimeric dyes reveals very strong propensities for self-assembly unlike their monomeric dye counterparts. The N-propyl linked dye exhibits pronounced H-aggregation at micromolar dye concentrations with the absorption maxima blue-shifted by nearly 200?nm. In contrast, an N-hexyl linked dye preferentially folds into H-dimers. Similar aggregates of the monomeric dicarbocyanine dyes are known to be observed at much higher dye concentrations or in presence of suitable templates such as DNA molecules. The aggregate species of the dimeric dyes are identified based on shifts in their absorbance maxima and quenched fluorescence. The calculated electronic structure of the dimeric dyes supports their observed aggregation behaviour. Further, introduction of DNA molecules with AT-tracts leads to transformation of the spontaneously formed dimeric dye H-aggregates and H-dimers into DNA-bound dye species.by Prathap Reddy Patlolla, Sairam S. Mallajosyula and Bhaskar Datt

An approach to rapid protein crystallization using nanodroplets

An approach that enables up to a two order of magnitude reduction in the amount of protein required and a tenfold reduction in the amount of time required for vapor-diffusion protein crystallization is reported. A prototype high-throughput automated system was used for the production of diffraction-quality crystals for a variety of proteins from a screen of 480 conditions using drop volumes as small as 20 nL. This approach results in a significant reduction in the time and cost of protein structure determination, and allows for larger and more efficient screens of crystallization parameter space. The ability to produce diffraction-quality crystals rapidly with minimal quantities of protein enables high-throughput efforts in structural genomics and structure-based drug discovery.</jats:p

Electron-beam-induced nanopatterning of J-aggregate thin films for excitonic and photonic response control

Excitons play a crucial role in the optical response of various materials. Molecular aggregates, such as J-aggregates, exhibit strong optical responses via exciton generation and coherent transport. Planar J-aggregate thin films can even show an optically metallic response in the visible region and may be considered as alternative materials for plasmonics. However, a direct method to control the optical properties of J-aggregate films using a top-down approach is not reported. Here, it is shown that the excitonic response of J-aggregate films can be locally modified by electron beam exposure, leading to a gradual change in the dielectric constant: from optically metallic (Re[epsilon] &lt; 0) to dielectric (Re[epsilon] &gt; 0). Nanoscale patterned films that exhibit clear polarization-dependent transmission and photoluminescence spectra are demonstrated. The remarkable spectral features can be attributed to the excitation of optical modes in excitonic films. This work suggests that nanopatterned excitonic films may be used as functional elements in various photonic systems to achieve the collaborative synergy between excitonic and photonic elements on a single platform