Hepatocyte growth factor (HGF) is a potent mitogen, motogen, and morphogen for various epithelial cell types. The pleiotropic effects of HGF are mediated by its binding to a specific high affinity receptor, c-Met. In addition, HGF binds to heparan sulfate proteoglycans on cell surfaces and within the extracellular matrix. Incubation of HGF with 0.1, 1.0, and 10 micrograms/ml of heparin, heparan sulfate, or dextran sulfate resulted in a concentration-dependent increase in mitogenic potency in a primary rat hepatocyte bioassay, whereas sodium sulfate or fucoidan did not. Although co-incubation of HGF with sulfated compounds that enhanced HGF-dependent mitogenesis did not alter the binding isotherm of HGF for the c-Met receptor in a solid phase assay, an increase in autophosphorylation of the c-Met receptor in intact A549 cells was observed upon their addition. A series of chemically sulfated malto-oligosaccharides varying in unit size and charge was tested in the bioassay in order to provide additional insights into the nature of the HGF-heparin interaction. While sulfated di-, tri-, tetra-, and pentasaccharides did not significantly potentiate HGF-dependent mitogenesis, larger oligosaccharides such as the sulfated hexa-, hepta-, or a sulfated oligosaccharide mixture containing decasaccharides resulted in an approximate 2-, 4-, and 7-fold enhancement, respectively. We observed a correlation between the sulfated oligosaccharide preparations that enhanced mitogenic potency and those that promoted HGF oligomerization in vitro, as measured by gel filtration and analytical ultracentrifugation. These findings indicate that heparin-like molecules can stabilize HGF oligomers, which may facilitate c-Met receptor dimerization and activation.

Binding proteins, thought to be auxin receptors, can be solubilised from maize (Zea mays L.) membranes after acetone treatment. From these crude extracts, receptor preparations of over 50% purity can be obtained by a reliable, straight-forward procedure involving three chromatographic steps - anion exchange, gel filtration and high-resolution anion exchange. Such preparations have been used to immunise rats for subsequent production of monoclonal antibodies. By the further step of native polyacrylamide gel electrophoresis the semi-purified preparations yield homogeneous, dimeric (22-kilodalton, kDa) auxin-binding protein, which has been used to produce a polyclonal rabbit antiserum. The preliminary characterisation of this antiserum and of the five monoclonal antibodies is presented. Two of the monoclonal antibodies specifically recognise the major 22-kDa-binding protein polypeptide whilst the other three recognise, in addition, a minor 21-kDa species. All the monoclonal antibodies recognise the polypeptide rather than the glycan side chain and the polyclonal antiserum also recognises deglycosylated binding protein. The antibodies have been used to quantify the abundance of auxinbinding protein in a number of tissues of etiolated maize seedlings. Root membranes contain 20-fold less binding protein than coleoptile membranes.

Functional polymorphism in the rat peptide transporter associated with antigen processing (TAP) changes the peptide pool available for binding and presentation by a class I MHC allele, RT1.Aa. The peptide binding motif for RT1.Aa, determined by stabilization with synthetic peptides, included a strong preference for arginine at the peptide C terminus. Analysis of natural peptides bound to RT1.Aa by both pool sequencing and anhydrotrypsin chromatography revealed that TAP polymorphism determined the presence or absence of arginine as the peptide C-terminal residue. This result highlights the in vivo impact of TAP-peptide selectivity, and provides evidence against a high rate of generation of new C termini by protease activity in the endoplasmic reticulum.

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Rewiring of cellular programs in malignant cells generates cancer-specific vulnerabilities. Here, using an unbiased screening strategy aimed at identifying non-essential genes required by tumor cells to sustain unlimited proliferative capacity, we identify the Male-Specific Lethal (MSL) acetyltransferase complex as a vulnerability of genetically unstable cancers. We find that disruption of the MSL complex and consequent loss of the associated H4K16ac mark do not substantially alter transcriptional programs, but compromise chromosome integrity and promote chromosomal instability (CIN) that progressively exhausts the proliferative potential of cancer cells through a p53-independent mechanism. This effect is dependent on pre-existing genomic instability and normal cells are insensitive to MSL disruption. Using cell-and patient-derived xenografts from multiple cancer types, we show that excessive CIN induced by MSL disruption inhibits tumor maintenance. Our findings suggest that targeting of MSL may be a valuable means to increase CIN beyond the level tolerated by cancer cells without inducing severe adverse effects in normal tissues.Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use: http://www.nature.com/authors/editorial_policies/license.html#terms