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The Adjuvant Action of Synthetic Polynucleotides on the Immune Response
Published in Edward P. Cohen, A. Arthur Gottlieb, Immune RNA, 2020
Polynucleotides are produced by the action on the respective mononucleotides of an enzyme, polynucleotide phosphorylase, isolated from Micrococcus lysodeikticus. In the presence of this enzyme, the mononucleotide groups are joined via 3′-5-phosphodiester linkages and polymerized. When the polynucleotides of two base pairs are mixed (e.g., polyadenylic acid with polyuridylic acid, poly A:U, or polyinosinic acid with polycytidylic acid, poly I:C) annealing occurs, and a helical conformation ensues. Copolymers with varying proportions of the different nucleotides (e.g., poly A-U or poly I-C) also can be synthesized in this manner.
RNA
Published in Paul Pumpens, Single-Stranded RNA Phages, 2020
Further development of the Qβ sequencing occurred in the obstacles of the gene engineering approaches. As in the case of the MS2 RNA, the Qβ RNA was extended at the 3′-end with the polyA segment by terminal riboadenylate transferase purified from calf thymus (Gilvarg et al. 1974, 1975a) The polyadenylated Qβ RNA retained full infectivity in a spheroplast assay system. However, the progeny viruses did not contain polyA termini, indicating an in vivo rectification of the in vitro alteration (Gilvarg et al. 1975a). While the polyA-Qβ RNA functioned normally as messenger for the synthesis of virus-specific proteins, it had lost its capacity to serve as template for the Qβ replicase. The template function was restored, however, by phosphorolysis with polynucleotide phosphorylase. It was concluded that a host enzyme, perhaps polynucleotide phosphorylase, removed part or all of the adenylate residues prior to replication of the RNA in vivo (Gilvarg et al. 1975b). The Qβ RNA was elongated also with a 3′-terminal oligoC tract (Mekler and Billeter 1975). Meanwhile, polyA sequences were added to the 3′-terminus of the Qβ RNA by ATP:RNA adenylyltransferase from E. coli by Fiers’ team (Devos et al. 1976c). By tail lengths not exceeding 200 nucleotide residues, the physical properties of Qβ-RNA-polyA were only slightly different from those of the original RNA, but almost complete abolishment of template activity, even by short oligoA stretches, was found, in agreement with the conclusions of Weissmann’ team.
Analysis of Small RNA Species: Phylogenetic Trends
Published in S. K. Dutta, DNA Systematics, 2019
Mirko Beljanski, Liliane Le Goff
Small RNAs can be synthesized de novo from ribonucleoside-5′-triphosphates by Escherichia coli Qβ replicase, an enzyme which also replicates Qβ RNA template, as well as satellite RNA of Qβ virion. Polynucleotide phosphorylase (PNPase) from bacteria can also synthesize RNA from ribonucleoside-5′-diphosphates.6 These facts and the observation that small RNAs from different origins can be transcribed into DNA, contribute to modifying notions about the origin and flow of information in cells. For these and other reasons, scientists have thus studied small RNAs and have visualized their possible participation in the creation of new genes and/or pseudogenes. In this chapter, we shall attempt to give an overview of many different small RNAs by describing their chemical and physical properties as well as their evident, or possible biological role. The phylogenetic trends between these RNAs will be evaluated on the basis of sequence data since at the present time the biological functions of the majority of small RNAs are unknown.
Recent advances in delivering RNA-based therapeutics to mitochondria
Published in Expert Opinion on Biological Therapy, 2022
Yuma Yamada, Sen Ishizuka, Manae Arai, Minako Maruyama, Hideyoshi Harashima
One approach to delivering nucleus-encoded RNA into the mitochondria is to use polynucleotide phosphorylase (PNPase) encoded by the PNPT1 gene, which is a native RNA transport enzyme that is located in the mitochondrial intermembrane space [61]. There is increasing evidence to show that PNPase is involved in the import of small RNAs into mitochondria [62,63]. Furthermore, the addition of a small stem-loop sequence to transcripts that do not usually transfer to mitochondria has been shown to facilitate the transport of these RNAs into mitochondria in a PNPase-dependent manner [51].