Crosslinking of ribosomal protein S18 to 16 S RNA in E.coli ribosomal 30 S subunits by the use of a reversible crosslinking agent: trans-diamminedichloroplatinum(II)

Renal epithelial gene expression profile and bismuth-induced resistance against cisplatin nephrotoxicity

Nephrotoxicity is the most important dose-limiting factor in cisplatin based anti-neoplastic treatment. Pretreatment with bismuth salts, used as pharmaceuticals to treat gastric disorders, has been demonstrated to reduce cisplatin-induced renal cell death in clinical settings and during in vivo and in vitro animal experiments. To investigate the genomic basis of this renoprotective effect, we exposed NRK-52E cells, a cell line of rat proximal tubular epithelial origin, to 33 mM Bi3for 12 hours, which made them resistant to cisplatin-induced apoptosis. Differentially expressed genes in treated and untreated NRK-52E cells were detected by subtraction PCR and microarray techniques. Genes found to be down regulated (0.17/0.31-times) were cytochrome c oxidase subunit I, BAR (an apoptosis regulator), heat-shock protein 70-like protein, and three proteins belonging to the translation machinery (ribosomal proteins S7 and L17, and S1, a member of the elongation factor 1-alpha family). The only up-regulated gene was glutathione Stransferase subunit 3A (1.89-times). Guided by the expression levels of these genes, it may be possible to improve renoprotective treatments during anti-neoplastic therapies.

Site-specific platinum(II) cross-linking in a ribozyme active site

The function of RNA depends on its ability to adopt complex and dynamic structures, and the incorporation of site-specific cross-linking probes is a powerful method for providing distance constraints that are valuable in RNA structural biology. Here we describe a new RNA-RNA cross-linking strategy based on Pt(II) targeting of specific phosphorothioate substitutions. In this strategy cis-diammine Pt(II) complexes are kinetically recruited and anchored to a phosphorothioate substitution embedded within a structured RNA. Substitution of the remaining exchangeable Pt(II) ligand with a nucleophile supplied by a nearby RNA nucleobase results in metal-mediated cross-links that are stable during isolation. This type of cross-linking strategy was explored within the catalytic core of the Hammerhead ribozyme (HHRz). When a phosphorothioate substitution is installed at the scissile bond normally cleaved by the HHRz, Pt(II) cross-linking takes place to nucleotides G8 and G10 in the ribozyme active site. Both of these positions are predicted to be within ~8 Å of a phosphorothioate-bound Pt(II) metal center. Cross-linking depends on Mg(2+) ion concentration, reaching yields as high as 30%, with rates that indicate cation competition within the RNA three-helix junction. Cross-linking efficiency depends on accurate formation of the HHRz tertiary structure, and cross-links are not observed for RNA helices. Combined, these results show promise for using kinetically inert Pt(II) complexes as new site-specific cross-linking tools for exploring RNA structure and dynamics.

TH1/TH2 paradigm in pregnancy: paradigm lost? Cytokines in pregnancy/early abortion: reexamining the TH1/TH2 paradigm

In this paper, we briefly survey the history of concepts in reproductive immunology from antibody-mediated tolerance to the "fetal allograft" to the current concept of an embryo "bathing in a sea of cytokines". We then review the paradigm that "allopregnancy is a Th2 phenomenon" and some of the evidence gained in animals and humans supporting it. We continue by discussing the light it sheds on immunologically caused recurrent abortion, and the present status of the concepts. We next show the limits of the Th1/Th2 paradigm by reviewing the role of "inflammatory" cytokines in implantation (as first seen with leukemia inhibitory factor). We go on to discuss recent data showing that interferon-gamma is not solely a "bad guy", e.g. abortifacient as the paradigm would predict, but is needed at low doses for the vascular development and transformation of uterine spiral arteries required for implantation and successful pregnancy. We conclude by discussing the emerging role of NK and IL-12, IL-15, IL-18 tripods and other cytokines in local angiogenesis and tissue remodelling, a series of new data bringing us well beyond the Th1/Th2 paradigm in pregnancy which, in this context, appears now obsolete and an oversimplification, although it has indeed been useful at first. Rather, step-specific events have to be considered and a key role is seen in local tissue remodelling, in which immune cytokines play an important role while not always being secreted by immune cells.

Topography of the Escherichia coli ribosomal 30S subunit-initiation factor 2 complex

The specific effect of the binding of initiation factor IF2 on E coli 16S rRNA within the [IF2/30S/GTP] complex has been probed by crosslinking experiment with trans-diamminedichloro platinum (II) and by phosphate alkylation with ethylnitrosourea. Several 16S rRNA fragments crosslinked to IF2 have been identified and are mostly located in the head and the lateral protrusion of the 30S subunit. The study of the effect of IF2 binding to the 30S subunit reveals that the factor does not tightly bind to the 16S rRNA and induces both isolated reductions and enhancements of phosphate reactivity in the 16S rRNA. Several of them are located near the binding site of IF2 and weak effects are observed in distant parts of the subunit. These results are discussed in the light of current knowledge of the topographical localization of IF2 with the 30S subunit and of its relation with function.

Differences in 23 S rRNA-protein neighbourhood in Escherichia coli 70 S ribosomes and 70 S initiation complex. Probing by bifunctional Pt(II)-containing reagent

rRNA-protein cross-links in free E. coli 35S-labeled 70 S ribosomes and in the initiation complex 35S-labeled 70 S ribosome.AUGU6.fMet-tRNA(fMet) were studied with the aid of a new type of binuclear Pt(II) compound - dichlorotetra-ammine(1,6-hexamethylenediaminediplatinum++ +) dichloride. The use of this reagent allowed us to reveal differences in the rRNA-protein neighbourhood in free 70 S ribosomes and in the initiation complex. Proteins L3, L6, L23 and L25 were shown to cross-link to 23 S rRNA only in the initiation complex, whereas proteins L1, L13, L14, L16, L17, L18, L22, L28 and S1 did so in both free ribosomes and the complex. 16 S rRNA was found to be cross-linked preferentially to a single protein, S1, in both states of the ribosomes.

Crosslinking of elongation factor Tu to tRNA(Phe) by trans-diamminedichloroplatinum (II). Characterization of two crosslinking sites on EF-Tu

In a preceding paper [(1987) Nucleic Acids Res. 15, 5787-5801], we have used trans-diamminedichloroplatinum (II) to induce reversible RNA-protein crosslinks within the ternary EF-Tu/GTP/Phe-tRNA(Phe) complex and have identified two crosslinking sites on the tRNA. The aim of the present paper is to determine the crosslinking sites on EF-Tu. Two tryptic peptides located in domain I could be identified, a major one (residues 45-74) and a minor one (residues 117-154). The use of Staphylococcus aureus V8 protease led to the isolation of two major peptides (residues 56-68 and 64-68) and one minor peptide (118-124). These results are discussed in the light of the current knowledge of the topography of the EF-Tu/tRNA complex.