RNA-dependent RNA polymerase

About: RNA-dependent RNA polymerase is a research topic. Over the lifetime, 13904 publications have been published within this topic receiving 767954 citations. The topic is also known as: RdRp & RNA replicase.

Persistent synthesis of 5S RNA when production of 28S and 18S ribosomal RNA is inhibited by low doses of actinomycin D.

Abstract: To determine whether transcription of the genes coding for 5S ribosomal RNA depends upon the concurrent activity of the genes for 28S and 18S ribosomal RNA we studied the synthesis of 5S RNA in cultured L cells when the synthesis of the 45S precursor of 28 and 18S RNA was inhibited with low doses of actinomycin D. Synthesis of 5S RNA was measured by following the incorporation of 3H uridine into components which, upon acrylamide gel electrophoresis, co-migrated with markers of 5S RNA obtained from 32P labeled ribosomes. We observed that the synthesis of 5S RNA persists in the absence of detectable 28S and 18S RNA synthesis, continuing at the normal rate for several hours and at a reduced rate for at least a generation time. This strongly supports the concept that 45S RNA is not a precursor of 5S RNA, and indicates furthermore that neither the 45S component, nor any of the intermediates involved in its transition to 28S and 18S RNA, are involved in controlling the output of the 5S genes The 5S RNA which is made during actinomycin treatment is retained predominantly in the nucleoplasm and undergoes a turnover of about 3.5% per hour. It apparently cannot be utilized when ribosome synthesis resumes following removal of the actinomycin.

Bacteriophage T4 RNA ligase 2 (gp24.1) exemplifies a family of RNA ligases found in all phylogenetic domains

Abstract: RNA ligases participate in repair, splicing, and editing pathways that either reseal broken RNAs or alter their primary structure. Bacteriophage T4 RNA ligase (gp63) is the best-studied member of this class of enzymes, which includes yeast tRNA ligase and trypanosome RNA-editing ligases. Here, we identified another RNA ligase from the bacterial domain—a second RNA ligase (Rnl2) encoded by phage T4. Purified Rnl2 (gp24.1) catalyzes intramolecular and intermolecular RNA strand joining through ligase-adenylate and RNA-adenylate intermediates. Mutational analysis identifies amino acids required for the ligase-adenylation or phosphodiester synthesis steps of the ligation reaction. The catalytic residues of Rnl2 are located within nucleotidyl transferase motifs I, IV, and V that are conserved in DNA ligases and RNA capping enzymes. Rnl2 has scant amino acid similarity to T4 gp63. Rather, Rnl2 exemplifies a distinct ligase family, defined by variant motifs, that includes the trypanosome-editing ligases and a group of putative RNA ligases encoded by eukaryotic viruses (baculoviruses and an entomopoxvirus) and many species of archaea. These findings have implications for the evolution of covalent nucleotidyl transferases and virus-host dynamics based on RNA restriction and repair.