Topic
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.
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TL;DR: It is demonstrated that baculovirus-expressed wild-type but not motif A mutated VP1 acts as an RdRp on IBDV-specific RNA templates and it has been demonstrated unequivocally that VP1 represents the RdRP of I BDV.
Abstract: Segment B of the bisegmented, double-stranded RNA genome of infectious bursal disease virus (IBDV) encodes the viral protein VP1. This has been presumed to represent the RNA-dependent RNA polymerase (RdRp) as it contains motifs that are typical for the RdRp of plus-strand RNA viruses. Here it is demonstrated that baculovirus-expressed wild-type but not motif A mutated VP1 acts as an RdRp on IBDV-specific RNA templates. Thus, on a plus-strand IBDV segment A cRNA template, minus-strand synthesis occurred in such a way that a covalently linked double-stranded RNA product was generated (by a 'copy-back' mechanism). Importantly, enzyme activity was observed only with templates that comprised the 3' non-coding region of plus-strand RNAs transcribed from IBDV segments A and B, indicating template specificity. RdRp activity was shown to have a temperature optimum of 37 degrees C and required magnesium ions for enzyme activity. Thus, it has been demonstrated unequivocally that VP1 represents the RdRp of IBDV.
159 citations
TL;DR: The structure of the reovirion was refined to a resolution of 7.6 Å by cryo-electron microscopy and three-dimensional image reconstruction, and polymerase λ3 was found anchored to the inner surface of the icosahedral core shell, suggesting how the nascent RNA is passed into the large external cavity of the pentameric capping enzyme complex formed by protein λ2.
Abstract: Reovirus is an icosahedral, double-stranded (ds) RNA virus that uses viral polymerases packaged within the viral core to transcribe its ten distinct plus-strand RNAs. To localize these polymerases, the structure of the reovirion was refined to a resolution of 7.6 A by cryo-electron microscopy (cryo-EM) and three-dimensional (3D) image reconstruction. X-ray crystal models of reovirus proteins, including polymerase λ3, were then fitted into the density map. Each copy of λ3 was found anchored to the inner surface of the icosahedral core shell, making major contacts with three molecules of shell protein λ1 and overlapping, but not centering on, a five-fold axis. The overlap explains why only one copy of λ3 is bound per vertex. λ3 is furthermore oriented with its transcript exit channel facing a small channel through the λ1 shell, suggesting how the nascent RNA is passed into the large external cavity of the pentameric capping enzyme complex formed by protein λ2.
159 citations
TL;DR: Subunit I of the RNA phage-specific Qβ replicase is shown to be identical with the Escherichia coli 30 S ribosomal protein Sl by the following criteria: ability to restore Qβ RNA-directed activity of Qβ Replicase lacking subunit I, immunological cross-reactivity, and identity of the first four amino acids at the NH2 terminus.
159 citations
TL;DR: The ability of certain small, circular, pathogenic RNAs of plants and animals to self-cleave at specific sites in vitro in the complete absence of protein most likely plays a central role in their replication in vivo by a rolling circle mechanism.
159 citations
TL;DR: The high-resolution crystal structure of a primase, comprising the catalytic core of the Escherichia coli DnaG protein, was determined and it is likely that DnG binds nucleic acid in a groove clustered with invariant residues and that DnuG is positioned within the replisome to accept single-stranded DNA directly from the replicative helicase.
Abstract: All cellular organisms use specialized RNA polymerases called "primases" to synthesize RNA primers for the initiation of DNA replication. The high-resolution crystal structure of a primase, comprising the catalytic core of the Escherichia coli DnaG protein, was determined. The core structure contains an active-site architecture that is unrelated to other DNA or RNA polymerase palm folds, but is instead related to the "toprim" fold. On the basis of the structure, it is likely that DnaG binds nucleic acid in a groove clustered with invariant residues and that DnaG is positioned within the replisome to accept single-stranded DNA directly from the replicative helicase.
159 citations