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  • Purification and functional characterization of a histone H3-lysine 4-specific methyltransferase. 11779497

    Methylation of histone H3 at lysine 9 by SUV39H1 and subsequent recruitment of the heterochromatin protein HP1 has recently been linked to gene silencing. In addition to lysine 9, histone H3 methylation also occurs at lysines 4, 27, and 36. Here, we report the purification, molecular identification, and functional characterization of an H3-lysine 4-specific methyltransferase (H3-K4-HMTase), SET7. We demonstrate that SET7 methylates H3-K4 in vitro and in vivo. In addition, we found that methylation of H3-K4 and H3-K9 inhibit each other. Furthermore, H3-K4 and H3-K9 methylation by SET7 and SUV39H1, respectively, have differential effects on subsequent histone acetylation by p300. Thus, our study provides a molecular explanation to the differential effects of H3-K4 and H3-K9 methylation on transcription.
    Tipo de documento:
    Referencia
    Referencia del producto:
    AB3353

  • Purification and characterization of enterovirus 71 viral particles produced from vero cells grown in a serum-free microcarrier bioreactor system. 21603631

    Enterovirus 71 (EV71) infections manifest most commonly as a childhood exanthema known as hand-foot-and-mouth disease (HFMD) and can cause neurological disease during acute infection.In this study, we describe the production, purification and characterization of EV71 virus produced from Vero cells grown in a five-liter serum-free bioreactor system containing 5 g/L Cytodex 1 microcarrier. The viral titer was greater than 10(6) TCID(50)/mL by 6 days post infection when a MOI of 10(-5) was used at the initial infection. Two EV71 virus fractions were separated and detected when the harvested EV71 virus concentrate was purified by sucrose gradient zonal ultracentrifugation. The EV71 viral particles detected in the 24-28% sucrose fractions had an icosahedral structure 30-31 nm in diameter and had low viral infectivity and RNA content. Three major viral proteins (VP0, VP1 and VP3) were observed by SDS-PAGE. The EV71 viral particles detected in the fractions containing 35-38% sucrose were 33-35 nm in size, had high viral infectivity and RNA content, and were composed of four viral proteins (VP1, VP2, VP3 and VP4), as shown by SDS-PAGE analyses. The two virus fractions were formalin-inactivated and induced high virus neutralizing antibody responses in mouse immunogenicity studies. Both mouse antisera recognized the immunodominant linear neutralization epitope of VP1 (residues 211-225).These results provide important information for cell-based EV71 vaccine development, particularly for the preparation of working standards for viral antigen quantification.
    Tipo de documento:
    Referencia
    Referencia del producto:
    MAB979
    Nombre del producto:
    Anti-Enterovirus 71 Antibody, cross-reacts with Coxsackie A16, clone 422-8D-4C-4D

  • Purification and characterization of proximal sequence element-binding protein 1, a transcription activating protein related to Ku and TREF that binds the proximal sequen ... 2211668

    The promoter structure of the known small nuclear RNA (snRNA) genes contains two major effectors of transcriptional activity, a proximal sequence element (PSE) and a distal sequence element (DSE). In previous work, methidiumpropyl-EDTA-Fe(II) footprinting was used to demonstrate the existence in human placental extracts of a protein producing footprints within the PSE and the DSE of the human U1 snRNA gene. This protein (PSE1) has now been purified to homogeneity from both human placental extract and K562 cell nuclear extract. PSE1 consists of two subunits, an alpha subunit with an apparent molecular mass of 83 kDa, and a beta subunit with an apparent molecular mass of 73 kDa in K562 nuclear extracts and 63 kDa in placental extracts. Footprinting and UV cross-linking assays indicate that purified PSE1 binds to the PSE and DSE of the U1 gene. Monoclonal antibodies were prepared which specifically recognize the individual subunits of PSE1. PSE1 is immunologically similar to and shares amino acid sequence with a protein (TREF) which binds the human transferrin receptor (HTFR) promoter. An in vitro transcription system was established for a template consisting of a minimal HTFR promoter placed upstream of the human U1 snRNA-coding region and shown by immunodepletion/addback experiments to specifically require PSE1. Transcription from the adenovirus 2 major late promoter was unaffected in these experiments. This result supports a functional role of PSE1 as a transcriptional activating protein, but its role in transcription of snRNA genes remains to be established. PSE1 also has an immunological relationship to and shares amino acid sequence with the p70 and p86 subunits of the human Ku autoantigen. Ku, PSE1, and TREF may thus be identical proteins or members of a family of heterodimeric proteins consisting of related subunits. Our results support earlier proposals that Ku may be a transcriptional activator.
    Tipo de documento:
    Referencia
    Referencia del producto:
    Múltiplo
    Nombre del producto:
    Múltiplo

  • Purification of an Elastin-Like Fusion Protein by Microfiltration 16767781

    This article describes a simple and potentially scalable microfiltration method for purification of recombinant proteins. This method is based on the fact that when an elastin-like polypeptide (ELP) is fused to a target protein, the inverse phase transition behavior of the ELP tag is imparted to the fusion protein. Triggering the phase transition of a solution of the ELP fusion protein by an increase in temperature, or isothermally by an increase in salt concentration, results in the formation of micron-sized aggregates of the ELP fusion protein. In this article, it is shown that these aggregates are efficiently retained by a microfiltration membrane, while contaminating E. coli proteins passed through the membrane upon washing. Upon reversing the phase transition by flow of Milli-Q water, soluble, pure, and functionally active protein is eluted from the membrane. Proof-of principle of this approach was demonstrated by purifying a fusion of thioredoxin with ELP (Trx-ELP) with greater than 95% recovery of protein and with greater than 95% purity (as estimated from SDS–PAGE gels). The simplicity of this method is demonstrated for laboratory scale purification by purifying Trx-ELP from cell lysate using a syringe and a disposable microfiltration cartridge. The potential scalability of this purification as an automated, continuous industrial-scale process is also demonstrated using a continuous stirred cell equipped with a microfiltration membrane.
    Tipo de documento:
    Referencia
    Referencia del producto:
    Múltiplo

  • Purification of a serine kinase that associates with and phosphorylates human Cdc25C on serine 216. 7982962

    Human Cdc25C is a protein phosphatase that dephosphorylates and activates Cdc2-cyclin B to trigger entry into mitosis. Cdc25C is itself regulated by phosphorylation. In asynchronously growing HeLa cells, we have determined that serine 216 is the major site of Cdc25C phosphorylation. We have isolated a protein kinase that binds to Cdc25C and phosphorylates serine 216. The kinase binds within amino acids 200-256 of Cdc25C. This region is conserved in some Cdc25 homologues and contains a putative bipartite nuclear localization signal just downstream from serine 216. Finally, the Cdc25C-associating kinase was purified over 8000-fold from rat liver as a 36-38-kDa doublet of proteins.
    Tipo de documento:
    Referencia
    Referencia del producto:
    05-680

  • Purification and reconstitution of sterol transfer by native mouse ABCG5 and ABCG8. 18402465

    ABCG5 (G5) and ABCG8 (G8) are ATP-binding cassette half-transporters that limit intestinal uptake and promote biliary secretion of neutral sterols. Here, we describe the purification of endogenous G5G8 from mouse liver to near homogeneity. We incorporated the native proteins into membrane vesicles and reconstituted sterol transfer. Native gel electrophoresis, density-gradient ultracentrifugation, and chemical cross-linking studies indicated that the functional native complex is a heterodimer. No higher order oligomeric forms were observed at any stage in the catalytic cycle. Sterol transfer activity by purified native G5G8 was stable, stereospecific, and selective. We also report that G5 but not G8 is S-palmitoylated and that palmitoylation is not essential for dimerization, trafficking, or biliary sterol secretion. Both G5 and G8 have short but highly conserved cytoplasmic tails. The functional roles of these C-terminal regions were examined using an in vivo functional assay.
    Tipo de documento:
    Referencia
    Referencia del producto:
    Múltiplo
    Nombre del producto:
    Múltiplo