Soy isoflavone supplementation in healthy men prevents NF-kappa B activation by TNF-alpha in blood lymphocytes.

Dietary intake of soy has been associated with a decreased risk of cancer. Soy isoflavones have been postulated to be the protective compounds in soybeans; however, the precise mechanism by which soy isoflavones prevent human cancer is not known. The major soy isoflavones, genistein and daidzein, are antioxidant compounds, therefore one possible mechanism of action is through their antioxidant effect. We have previously demonstrated that the soy isoflavone, genistein, inhibits the activation of the redox-sensitive transcription factor, NF-kappa B, in prostate cancer cells in vitro. In this study, we have demonstrated that genistein, but not daidzein, inhibits TNF-alpha-induced NF-kappa B activation in cultured human lymphocytes. Additionally, we investigated the in vivo effect of soy isoflavone supplementation on NF-kappa B activation induced by TNF-alpha in vitro in peripheral blood lymphocytes of six healthy men. We show that healthy male subjects receiving 50 mg isoflavone mixture (Novasoy) twice daily for 3 weeks are protected from TNF-alpha induced NF-kappa B activation. Additionally, we observed a reduction of 5-hydroxymethyl-2'-deoxyuridine (5-OHmdU), a marker for oxidative DNA damage, following isoflavone supplementation. The inhibitory effect of soy isoflavones was no longer present 3 months after the supplementation. This preliminary study demonstrates that soy isoflavone supplementation may protect cells from oxidative stress-inducing agents by inhibiting NF-kappa B activation and decreasing DNA adduct levels.

ETO-2, a new member of the ETO-family of nuclear proteins.

The t(8;21) is associated with 12-15% of acute myelogenous leukemias of the M2 subtype. The translocation results in the fusion of two genes, AML1 (CBFA2) on chromosome 21 and ETO (MTG8) on chromosome 8. AML1 encodes a DNA binding factor; the ETO protein product is less well characterized, but is thought to be a transcription factor. Here we describe the isolation and characterization of ETO-2, a murine cDNA that encodes a new member of the ETO family of proteins. ETO-2 is 75% identical to murine ETO and shares very high sequence identities over four regions of the protein with ETO (domain I-III and zinc-finger). Northern analysis identifies ETO-2 transcripts in many of the murine tissues analysed and in the developing mouse embryo. ETO-2 is also expressed in myeloid and erythroid cell lines. We confirmed the nuclear localization of ETO-2 and demonstrated that domain III and the zinc-finger region are not required for nuclear localization. We further showed that a region within ETO, containing domain II, mediates dimerization among family members. This region is conserved in the oncoprotein AML-1/ETO. The recent identification of another ETO-like protein, myeloid translocation gene-related protein 1, together with the data presented here, demonstrates that at least three ETO proteins exist with the potential to form dimers in the cell nucleus.

Glycine reductase protein C. Properties and characterization of its role in the reductive cleavage of Se-carboxymethyl-selenoprotein A.

The clostridial glycine reductase complex catalyzes the reductive deamination of glycine in an energy-conserving process that results in the esterification of orthophosphate. The complex consists of three protein components: selenoprotein A; protein B, a carbonyl group protein; and protein C, a sulfhydryl protein. The protein C component also catalyzes the arsenate-dependent decomposition of acetyl phosphate. Reaction of protein C with iodoacetate inhibits its ability to decompose acetyl phosphate, but this inactivation of the enzyme by alkylation is prevented in the presence of the substrate indicating the formation of an unreactive enzyme-bound acetylthiol ester. The Se-carboxy-methylselenocysteine residue of the selenoprotein A component of glycine reductase was generated by selective alkylation of the ionized selenol group at pH 6 with [14C]bromoacetate. Using this pure alkylated selenoprotein A as substrate, it was shown that protein C catalyzes the conversion of the [14C]carboxymethyl group, in selenoether linkage to protein A, to [14C]acetate in the presence of arsenate, dithiothreitol, and Mg2+. A procedure using hydrophobic chromatographic matrices was developed for the large scale isolation of protein C, and a number of the properties of the enzyme were determined.

Amino acid sequence analysis of Escherichia coli formate dehydrogenase (FDHH) confirms that TGA in the gene encodes selenocysteine in the gene product.

The formate dehydrogenase (FDHF) of Escherichia coli is a selenocysteine-containing protein that occurs as a component of the formate-hydrogen lyase complex. The gene encoding this 80 kd polypeptide contains a TGA codon in the open reading frame. Several indirect lines of evidence showed earlier that the selenocysteine residue in the protein is inserted co-translationally in a TGA (UGA) dependent process. Direct proof that the selenocysteine is present in the polypeptide in the position corresponding to TGA as predicted from the gene sequence was obtained by automated amino acid sequence analysis of a 75Se-containing peptide isolated from the protein. Construction of a fusion gene comprising a small segment of the fdhF gene linked to the lacZ gene as reporter greatly facilitated isolation of the selenocysteine-containing protein. Subsequent cleavage of this isolated gene product with endoproteinase Asp-N gave rise to an easily purified small selenocysteine-containing peptide that was amenable to amino acid sequence analysis.

Large-dose infusions of heparinoid ORG 10172 in ischemic stroke.

We evaluated the safety and possible efficacy of large doses of the heparinoid ORG 10172 in 57 patients with acute or progressing ischemic stroke. Patients received a loading bolus of the drug followed by a maintenance intravenous infusion for 7 days. The plasma level of ORG 10172 was monitored by the degree of inhibition of coagulation factor Xa. In general, the drug was well tolerated and few hemorrhagic complications occurred. Two patients with large cardioembolic hemispheric strokes had intracranial hemorrhagic complications. Most patients improved during treatment. By 3 months after the stroke, 37 patients (65%) had a favorable outcome (minimal or no residual disability). This study suggests that high-dose intravenous infusions of ORG 10172 can be safely given to patients with acute ischemic stroke.

Identification of a selenocysteyl-tRNA(Ser) in mammalian cells that recognizes the nonsense codon, UGA.

The presence of a unique opal suppressor seryl-tRNA in higher vertebrates which is converted to phosphoseryl-tRNA has been known for several years, but its function has been uncertain (see Hatfield, D. (1985) Trends Biochem. Sci. 10, 201-204 for review). In the present study, we demonstrate that this tRNA species also occurs in vivo as selenocysteyl-tRNA(Ser) suggesting that it functions both as a carrier molecule upon which selenocysteine is synthesized and as a direct selenocysteine donor to a growing polypeptide chain in response to specific UGA codons. [75Se]Seleno[3H]cysteyl-tRNA(Ser) formed by administering 75Se and [3H]serine to rat mammary tumor cells (TMT-081-MS) in culture was isolated from the cell extract. The amino acid attached to the tRNA was identified as selenocysteine following its deacylation and reaction with iodoacetate and 3-bromopropionate. The resulting alkyl derivatives co-chromatographed on an amino acid analyzer with authentic carboxymethylselenocysteine and carboxyethylselenocysteine. Seryl-tRNA(Ser) and phosphoseryl-tRNA(Ser) (Hatfield, D., Diamond, A., and Dudock, B. (1982) Proc. Natl. Acad. Sci. U. S. A. 79, 6215-6219), which co-migrate on a reverse phase chromatographic column with selenocysteyl-tRNA(Ser), were also identified in extracts of TMT-018-MS cells. Hence, we propose that a metabolic pathway for selenocysteine synthesis in mammalian cells is the conversion of seryl-tRNA(Ser) via phosphoseryl-tRNA(Ser) to selenocysteyl-tRNA(Ser). In a ribosomal binding assay selenocysteyl-tRNA(Ser) recognizes UGA but not any of the serine codons. Selenocysteyl-tRNA(Ser) is deacylated more readily than seryl-tRNA(Ser) (i.e. 58% deacylation during 15 min at pH 8.0 and 37 degrees C as compared to 41%).

Biochemical and genetic analysis of Salmonella typhimurium and Escherichia coli mutants defective in specific incorporation of selenium into formate dehydrogenase and tRNAs.

Mutation of a single gene, referred to as selA1 in Salmonella typhimurium and as selD in Escherichia coli, results in the inability of these organisms to insert selenium specifically into the selenopolypeptides of formate dehydrogenase and into the 2-selenouridine residues of tRNAs. The mutation does not involve transport of selenite into the cell or reduction of selenite to selenide since both mutant strains synthesize selenocysteine and selenomethionine from added selenite and incorporate these selenoamino acids non-specifically into numerous proteins of the bacterial cells. Complementation of the mutation in S. typhimurium with the selD gene from E. coli indicates functional identity of the selA1 and selD genes. Although the selA1 gene maps at approximately 21 min on the S. typhimurium chromosome and the selD gene at approximately 38 min on the E. coli chromosome, only a single gene in wild-type S. typhimurium hybridized to the E. coli selD gene probe. Transformation of the mutant Salmonella strain with a plasmid bearing the E. coli selD gene restored formate dehydrogenase activity, 75Se incorporation into formate dehydrogenase seleno-polypeptides and [75Se]seleno-tRNA synthesis. Transformation with an additional plasmid carrying an E. coli formate dehydrogenase selenopolypeptide-lacZ gene fusion showed that the selD gene allowed readthrough of the UGA codon and synthesis of beta-galactosidase in the Salmonella mutant.

[3H]dihydroergocryptine binding in rat brain.

[3H]dihydroergocryptine (DHE) appears to bind to alpha-adrenergic receptor sites in rabbit uterine membranes. We have characterized the binding of [3H]DHE to membranes prepared from rat cerebral cortex. alpha-Adrenergic agents were less potent and dopamine and serotonin, more potent, in displacing brain DHE binding than in uterus. Furthermore brain DHE binding sites demonstrated less stereospecificity for catecholamines than sites in uterus. Dopamine displaced DHE binding with about the same potency in cerebellar and cerebral cortical membranes, but was 10 times as potent in displacing DHE binding in the striatum. The binding of [3H]DHE in brain is complex and differs significantly from the rabbit uterus. There are two possible explanations for this discrepancy. [3H]DHE may bind a single site in brain with properties differing from known peripheral adrenergic receptors or DHE may bind to multiple sites in brain, sites which may or may not represent other neurotransmitter receptors.

Chemical characterization of the selenoprotein component of clostridial glycine reductase: identification of selenocysteine as the organoselenium moiety.

A small, heat-stable selenoprotein, one of the components of the glycine reductase complex, was labeled with 75Se by growth of Clostridium sticklandii in the presence of Na2 75SeO3. The selenium-containing moiety, which is essential for the biological activity of the protein, was shown to be a selenocysteine residue. It was isolated as its Se-carboxymethyl, Se-carboxyethyl, and Se-aminoethyl derivatives from digests of the pure 75Se-labeled protein that had been reduced and treated with the various alkylating agents prior to hydrolysis. In each instance the 75Se-labeled moiety obtained from an alkylated protein sample and the corresponding alkyl derivative of authentic selenocysteine were indistinguishable. Several studies of the native selenoprotein detected a chromophore (UVmax 238nm) that appeared upon reduction of the protein with KBH4 and rapidly disappeared upon exposure to oxygen. This oxygen-labile chromophore is thought to be the ionized -SeH group of the selenocysteine residue.