Disease relevance of RNA1

• These results showed that RNA1 was required neither for virion assembly nor for maturation of provirions [1].
• However, capsid protein synthesized in cis from replicating RNA2 packaged RNA2 efficiently in the presence and absence of RNA1 [2].
• Flock House virus (FHV; Nodaviridae) is a positive-strand RNA virus that encapsidates a bipartite genome consisting of RNA1 and RNA2 [3].
• Flock house virus is a small insect virus with a bipartite RNA genome consisting of RNA1 and RNA2 [4].
• In Brome mosaic virus (BMV), genomic RNA1 (gB1) and RNA2 (gB2), encoding the replication factors, are packaged into two separate virions, whereas genomic RNA3 (gB3) and its subgenomic coat protein (CP) mRNA (sgB4) are copackaged into a third virion [5].

High impact information on RNA1

• Hsp90 inhibitors also suppressed viral RNA and protein A accumulation in S2 cells expressing an FHV RNA replicon [6].
• We investigated the role of the cellular chaperone heat shock protein 90 (Hsp90) in viral RNA replication complex assembly and function using Flock House virus (FHV), an alphanodavirus whose RNA-dependent RNA polymerase, protein A, is essential for viral RNA replication complex assembly on mitochondrial outer membranes [6].
• Long-distance base pairing in flock house virus RNA1 regulates subgenomic RNA3 synthesis and RNA2 replication [7].
• Protease digestion and selective permeabilization after differential epitope tagging demonstrated that protein A was inserted into the outer mitochondrial membrane with the N terminus in the inner membrane space or matrix and that the C terminus was exposed to the cytoplasm [8].
• Confocal immunofluorescence revealed that protein A localized to mitochondria in yeast, as in Drosophila cells, and that this mitochondrial localization was independent of viral RNA synthesis [8].

Biological context of RNA1

• Transcription of these plasmids in cells recreated the replication of PaV RNA1 and RNA2, synthesis of subgenomic RNA3, and translation of viral proteins A and alpha [9].
• However, RNA1 replication ceases ca. 3 days after transfection despite the presence of replication-competent RNA [10].
• DNA-Directed expression of functional flock house virus RNA1 derivatives in Saccharomyces cerevisiae, heterologous gene expression, and selective effects on subgenomic mRNA synthesis [11].
• The nodavirus flock house virus (FHV) has a bipartite, positive-sense, RNA genome that encodes the catalytic subunit of the RNA replicase and the viral capsid protein precursor on separate genomic segments (RNA1 and RNA2, respectively) [10].
• RNA1 can replicate autonomously when transfected into permissive cells, allowing study of the kinetics of RNA1 replication in the absence of either RNA2 or capsid proteins [10].

Anatomical context of RNA1

• AHNV RNA replication in the fish cell-line SSN-1 (derived from striped snakehead) was analysed by Northern blot analysis, which indicated that RNA3 was synthesised in large amounts (compared to RNA1) at an early point in time post-infection [12].

Associations of RNA1 with chemical compounds

• We have cloned and sequenced RNA1 from the Atlantic halibut Hippoglossus hippoglossus nodavirus (AHNV), and for the first time, the sequence of a betanodaviral subgenomic RNA3 has been determined [12].
• Nycodenz gradient flotation and dissociation assays showed that protein A behaved as an integral membrane protein, a finding consistent with a predicted N-proximal transmembrane domain [8].
• Confocal immunofluorescence microscopy and virus-specific, actinomycin D-resistant bromo-UTP incorporation identified mitochondria as the intracellular site of protein A localization and viral RNA synthesis [13].

Analytical, diagnostic and therapeutic context of RNA1

• Predicted domains for six RNA-dependent RNA polymerase motifs and putative ORFs (protein B) are confirmed by sequence analysis of WhNV RNA1 [14].
• Flotation and immunofluorescence studies with deletion mutants indicated that the N-proximal region of protein A was important for both membrane association and mitochondrial localization [8].
• Selective membrane permeabilization and immunoelectron microscopy further localized protein A to outer mitochondrial membranes [13].
• We detected protein A within 4 h after infection of Drosophila DL-1 cells and, by differential and isopycnic gradient centrifugation, found that protein A was tightly membrane associated, similar to integral membrane replicase proteins from other positive-strand RNA viruses [13].

References