Ribosome-inactivating proteins, similar to those already known [Barbieri & Stirpe (1982) Cancer Surveys 1, 489-520] were purified from the seeds of Saponaria officinalis (two proteins), of Agrostemma githago (three proteins), and of Asparagus officinalis (three proteins), and from the latex of Hura crepitans (one protein). The yield ranged from 8 to 400 mg/100 g of starting material. All proteins have an Mr of approx. 30000 and an alkaline isoelectric point. Their sugar content varies from 0 (proteins from S. officinalis) to 40% (protein from H. crepitans). The ribosome-inactivating proteins inhibit protein synthesis by rabbit reticulocyte lysate, the ID50 (concentration giving 50% inhibition) ranging from 1 ng/ml (a protein from S. officinalis) to 18 ng/ml (a protein from A. githago). Those which were tested (the proteins from S. officinalis and from A. githago) also inhibit polymerization of phenylalanine by isolated ribosomes, acting in an apparently catalytic manner. The protein from H. crepitans inhibited protein synthesis by HeLa cells, with an ID50 of 4 micrograms/ml, whereas the proteins from S. officinalis and from A. githago had an ID50 of more than 50-100 micrograms/ml. The ribosome-inactivating proteins from S. officinalis and from A. githago reduced the number of local lesions by tobacco-mosaic virus in the leaves of Nicotiana glutinosa.

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The single-chain ribosome-inactivating proteins (scRIPs) The so-RIPs asparin 1, dianthin 30, gelonin, momordin, PAP-S identified and mapped in pBR322.(pokeweed antiviral protein from Phytolacca americana seeds) and saporin 6 were highly purified as described previously [15]. HPLCpurified saporin 6, whose specific N-glycosidase activity had been Agarose and acrylamide/bis-acrylamide for gel electrophoresis were to the A-chains of ricin and related toxins [2], which are purchased from Clontech Laboratories, Palo Alto, CA (USA). All known to depurinate the ribosomal RNA by cleaving the Nother chemicals were of analytical grade.glycosidic bond in the A4324 position of the 28S RNA fracRestriction nucleases employed were: PvuII (from Proteus vulgaris) tion, so rendering it incapable of binding to the elongation incubation buffer: Tris-HCl 10 raM, NaC1 100 mM, MgCI2 10 mM, factors, with the consequent arrest of protein synthesis [3,4]. dithioerythritol 1 mM, pH 7.5 at 37°C; PstI (from Providencia stuartii) and HinfI (from Haemophylus influenzae Rf) incubation buffer: These proteins have attracted interest in the construction of Tris-HC1 50 mM, NaCI 10 raM, MgCI2 10 mM, dithioerythritol 1 immunotoxins after conjugation with monoclonal antibodies raM, pH 7.5 at 37°C; BamHI (from Bacillus amyloliquefacens H) for the selective killing of neoplastic cells [5 7].and HindIII (from Haemophylus influenzae Rd com-10) incubation To better understand perspectives and limits of the sc-RIPs buffer: Tris-HC1 10 mM, NaC1 100 raM, MgCI2 5 mM, 2-mercaptoethanol 1 mM, pH 8 at 37°C. in clinical trials, we previously focused our attention on the antiproliferative effect of RIPs as native molecules or in corn-2.2. DNase activity assay bination with other drugs. We have demonstrated that the pBR322 and OX174 plasmid DNA (250 ng), single-stranded M13 native form of the sc-RIP saporin 6 exerts an antiproliferative phage, lambda phage DNA, linearized plasmid DNA (250 ng) were incubated with or without various amounts (250-0.25 ng) of the dieffect in vitro in human breast cancer, leukemia and melanoverse proteins in a final volume of 10 ~tl at 37°C for various times. The ma cells to a very different extent and with diverse kinetics, reactions were carried out in a range of 5 60 mM NaC1 (or MgC12), l dependent on the specific cell target analyzed [8][9][10]. The efmM Tris-HC1, 0.1 mM EDTA. The range of pH was 6.5-8. At the fect may be potentiated by other drugs: a strong synergism end of the incubations, all the samples were extracted with phenol has been obtained by combination of saporin 6 with lonidfollowed by ether and precipitated [17]. Digestion with restriction endonucleases was carried out as specified above. The samples were amine in breast cancer cells in vitro [11]. More recent results analyzed in 0.8% agarose and/or in 6% polyacrylamide gel electroobtained by others also suggest a possible penetration of the phoresis. DNA bands were visualized by staining with ethidium brosc-RIPs into cells [12,13]. In the light of our resu...

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Cholesterol esterification by acyl-CoA:cholesterol acyltransferase (ACAT) and proliferation of vascular smooth muscle cells (VSMC) are key events in vascular proliferative diseases. Here we performed experiments to ascertain the role of cholesterol ester pathway in the control of human aortic VSMC cycle progression. Results showed that serum-induced VSMC proliferation was preceded by an increased ability of the cells to esterify cholesterol as well as by an increased expression of ACAT and multidrug resistance (MDR1) mRNAs and extracellular related kinases 1/2 (ERK1/2), whereas caveolin-1 levels were markedly decreased. Cell cycle analyses performed in the presence of two inhibitors of cholesterol esterification, directly inhibiting ACAT (Sandoz 58-035) or the transport of cholesterol substrate from plasma membrane to endoplasmic reticulum (progesterone), indicate that each inhibitor suppressed the serum-induced DNA synthesis by accumulation of VSMCs in the G1 phase. The effect was associated with a rapid inhibition of ERK1/2 mitogenic signaling pathway; a down-regulation of cyclin D1, ACAT, and MDR1 mRNA; and an up-regulation of caveolin-1. These data provide a plausible link between cholesterol esterification and control of cell cycle G1/S transition, supporting the hypothesis that cholesterol esterification may accelerate the progression of human vascular proliferative diseases by modulating the rate of the VSMC proliferation.