Solid-phase synthesis of oligoribonucleotides

An efficient method is described for solid-phase synthesis of oligoribonucleotides that involves use of the 9-fluorenylmethoxycarbonyl group (Fmoc) for 5'-protection, 4-methoxytetrahydropyran-4-yl (Mthp) for 2'-protection and a phosphoramidite coupling procedure.     

Solid-phase synthesis of oligoribonucleotides

Selective deprotection of the 5'-O-dimethoxytrityl group of oligoribonucleotides required for 5'-deprotection reaction during synthesis of an oligoribonucleotide was achieved by the treatment with 1% dichloroacetic acid in dichloromethane at room temperature, without removal of the 2'-O-tetrahydropyranyl group. Phosphorylation of protected ribonucleosides and coupling reaction to the 5' end of oligoribonucleotides attached to polystyrene solid support were carried out by the use of bifunctional reagent 2-chlorophenyl-O-O-bis(1-benzotriazolyl) phosphate. In this way, trinucleotides; TpTpT, dUpdUpT, and UpUpT, were synthesized.     

A new approach to the synthesis of branched and branched cyclic oligoribonucleotides.

The six-step synthesis of the di-triethylammonium salt of 5[prime]-O -trityl-6-N-pivaloyladenosine-2[prime]-(H -phosphonate)-3'-[(2-chlorophenyl) phosphate]9 from 3', 5'- O -(1,1,3,3-tetraisopropyldisiloxan-1,3-diyl)-6-N-pivaloyla denosine1in 68% overall yield is described. Compound9is converted into a branched pentaribonucleoside tetraphosphate 24 and a branched cyclic pentaribonucleotide ('lariat') 25 by solution phase triester chemistry involving both H-phosphonate and conventional phosphotriester coupling reactions. The monomeric building block 9 is proposed as a universal synthon for the preparation of branched and branched cyclic oligoribonucleotides derived from adenosine.     

Chemical synthesis of branched RNA.

A branched tetranucleotide consisting of adenosine linked 2' and 5' to guanosine and 3' to cytidine was synthesized from appropriately protected nucleoside phosphoramidites as synthons. The product was characterized enzymatically.     

Solid-phase synthesis of oligoribonucleotides using 9-fluorenylmethoxycarbonyl (Fmoc) for 5''-hydroxyl protection.

Efficient solid-phase synthesis of a series of oligoribonucleotides of up to 20 residues is described that utilises the 9-fluorenylmethoxycarbonyl group (Fmoc) for 5'-protection and 4-methoxytetrahydropyran-4-yl (Mthp) for 2'-protection of ribonucleotide monomers and a phosphoramidite coupling procedure. The Fmoc group is removed after each coupling step by treatment with 0.1M DBU in acetonitrile. Oligoribonucleotides are isolated in 2'-protected form in good yield and shown to be readily and efficiently deprotected by mild acidic treatment.     

Sequential formation of two branched intermediates during protein splicing of class three inteins

Extremophiles - Inteins are the protein equivalent of introns. They are seamlessly removed during post-translational maturation of their host protein (extein). Inteins from extremophiles played a...     

Solid-phase oligosaccharide synthesis and related technologies

Research efforts directed at the development of methodologies effective for solid-phase synthesis of oligosaccharides have resulted in a number of impressive achievements. In addition, closely related technologies, such as soluble polymer-supported synthesis and fluorous synthesis of the same class of molecules, have proved to be quite promising.     

The synthesis and processing of a nuclear RNA precursor to rat pregrowth hormone messenger RNA.

A recombinant DNA plasmid, pBR322-GH1, which contains about 80% of the sequences of rat pregrowth hormone (pGH) mRNA, allowed an analysis of nuclear RNA from GH3 cells for possible precursors of cytoplasmic pGH mRNA. A single 20-22S RNA SPECIES ABOUT 2-3 TIMes larger than pGH mRNA was detected in nuclear RNA from GH3 cells labeled for 5 min. with 3H-uridine. After longer label times a 12S RNA indistinguishable in size from cytoplasmic 12S pGH mRNA became the predominant labeled RNA complementary to the plasmid pBR322-GH1. Both of these nuclear RNA species contained poly (A). Kinetic analysis of the labeling of nuclear and cytoplasmic pGH mRNA sequences showed that the 20S and 12S nuclear RNA molecules were labeled before significant labeling of cytoplasmic pGH mRNA was detected, and also indicated that there is complete conservation of nuclear pGH mRNA sequences in the production of cytoplasmic pGH mRNA. These results indicate that cytoplasmic pGH mRNA is generated by nuclear processing of a larger nuclear RNA molecule.     

Regulation of HSP70 synthesis by messenger RNA degradation.

When Drosophila cells are heat shocked, hsp70 messenger RNA (mRNA) is stable and is translated at high efficiencies. During recovery from heat shock, hsp70 synthesis is repressed and its messenger RNA (mRNA) is degraded in a highly regulated fashion. Dramatic differences in the timing of repression and degradation are observed after heat treatments of different severities. The 3' untranslated region (UTR) of the hsp70 mRNA was sufficient to transfer this regulated degradation to heterologous mRNAs. Altering the translational efficiency of the message or changing its natural translation-termination site did not alter its pattern of regulation, although in some cases it changed the absolute rate of degradation. We have previously shown that hsp70 mRNA is very unstable when it is expressed at normal growth temperatures (from a metallothionein promoter). We report here that the 3' untranslated region of the hsp70 mRNA is responsible for this instability as well. We postulate that a mechanism for degrading hsp70 mRNA pre-exists in Drosophila cells, that it is inactivated by heat shock and that it is the reactivation of this mechanism that is responsible for hsp70 repression during recovery. This degradation system may be the same as that used by other unstable mRNAs.     

Solid-phase synthesis and biological evaluation of a uridinyl branched peptide urea library

A 1000-member uridinyl branched peptide library was synthesized on PS-DES support using IRORI technology. High-throughput screening of this library for anti-tuberculosis activity identified several members with a MIC₉₀ value of 12.5 μg/mL.     

New approach to automated synthesis of oligoribonucleotides

The combination of 2'-OH protection in ribonucleosides by the p-nitrophenylethylsulfonyl (NPES) group with the 3'-(beta-cyanoethyl) (N,N-diisopropyl)-phosphoramidite function reveals a new approach to oligoribonucleotide synthesis. The corresponding adenosine and guanosine derivatives have been applied to automated solid phase synthesis with good success.     

RNA ligase from bacteriophage T4. VIII. Solid phase enzymatic synthesis of oligoribonucleotides]

A method of the solid-phase enzymic synthesis of oligoribonucleotides has been suggested. The donor is fixed through its 3'-end on a water-insoluble matrix followed by the stepwise RNA ligase- and T4 polynucleotide kinase-assisted coupling of trinucleoside diphosphates in the 5'-direction. As an example, (pA)6pAox was immobilised on Biogel P-300 hydrazine and the RNA ligase-catalyzed addition of acceptor ApApA to the donor gave (Ap)9 with the 50% yield.     

Effect of the hepatocarcinogen ethionine on hepatic messenger RNA synthesis.

An experiment was conducted to determine if any changes resulted in the proportion of hepatic messenger RNA following treatment with ethionine, a hepatocarcinogen. The relative specific activity of the total RNA isolated from nontumor-like tissues was increased in Sprague-Dawley rats fed ethionine. However, the percentage of total RNA that was message was found to be decreased in the ethionine-treated rats.