Maria A. Siwecka

Effect of rye embryo ribosome nuclease on double-stranded RNA

Abstract In extracts obtained by treating rye embryo ribosomes with 0.5 M NH 4 Cl, nuclease activity was noted towards double-stranded RNA from virus of Penicillium chrysogenum and towards synthetic poly (A)-poly (U) and poly (I)-poly (C) complexes.

Synthesis, biological properties and anti-HIV-1 activity of new pyrimidine P1,P2-dinucleotides.

New homo- and hetero-P1,P2-dinucleotides were prepared with the use of multistep procedures starting from the monophosphates of 3′-fluoro-2-thiothymidine, 3′-fluoro-4-thiothymidine, AZT and 1-[(2-hydroxyethoxy)-methyl-5-propyl-6-phenylselenenyl]uracil. Anti-HIV properties of the synthesized P1,P2-dinucleotides were evaluated against laboratory syncytia inducing strain HIV-1 in CEM-T4 cells. Anti-HIV activities were in the range of 5–45 nM, and therapeutic indexes were higher than 4666–14000. Interactions of the above mentioned compounds with recombinant HIV-1 reverse transcriptase were also investigated. The obtained results point to reverse transcriptase inhibition, with somewhat lower inhibitory activity than that of their parental nucleoside-5′-triphosphates. Compound 6 may be regarded as a potent anti-HIV/AIDS drug.

Thiated Analogues of 2′,3′-Dideoxy-3′-fluorothymidine and Their Phosphorylated and Phosphonylated Derivatives: Synthesis, Interaction with HIV Reverse Transcriptase, and In Vitro Anti-HIV Activity

The search for new, modified 20,30-dideoxynucleosides, potential reverse transcriptase (RT) inhibitors, is still of special interest; bone marrow toxicity and rapidly developing resistance of currently used nucleosides point to the need for new RT inhibitors. 20,30-Dideoxy-30-fluorothymidine (FLT), a pyrimidine 30-deoxy30-substituted thymidine analogue, is one of the most potent in vitro inhibitors of HIV and its reverse transcriptase, but exhibits hematologic toxicity in vivo. It was previously shown that some 5-substituted 20,30-dideoxyuridine derivatives exhibited more selective anti-HIV activity. It appeared to us that an introduction to FLT of the substituents decreasing the pKa value for dissociation of N(3)-H, and enhancing hydrophobic properties of pyrimidine moiety may affect its inhibitory properties, with improved selectivity. It was therefore of interest to synthesize and to test the activity and cytotoxicity of hydrophobic analogues of FLT, and investigate its

Ribosomal Nuclease with Activity Towards Double-Stranded RNA

Ribonucleolytic activity has been suggested to be associated with plant ribosomes, but its role has not been elucidated (Hsiao 1968, Farkas 1982). According to Wilson (1982) nucleolytic ribosomal enzymes represent only a small fraction of the total nucleolytic activity of plant tissues. In our earlier investigations ribonucleolytic activity has been observed in nuclei, plastids, mitochondria, postribosomal supernatant and cytoplasmic ribosomes of rye embryos and 24-h seedlings. Specific ribonucleolytic activity was highest in the ribosome fraction from dry rye embryos (Siwecka et al., 1971). We have further demonstrated that deoxyribonucleolytic activity is also associated with rye embryo ribosomes. Both these activities are strongly associated with ribosomes and their subunits but a part of activity may be released by washing with 0.5 M ammonium chloride or 4 M urea (Siwecka et al., 1979). The NH4Cl ribosomal wash seems to contain an enzyme hydrolyzing double-stranded RNA, namely, double-stranded viral RNA from Penicillium chrysbgenum and the double-stranded poly(A)*poly(U) complex (Siwecka et al., 1982). So far there have been no reports on isolation from higher plants of enzymes hydrolyzing double-stranded RNA.