STRESS GRANULES AND PROCESSING BODIES IN REPLICATION-TRANSCRIPTION COMPLEX ACTIVITY Stress granules and processing (P) bodies are cytoplasmic RNA granules that contain translationally silenced messenger ribonucleoproteins, contributing to translation regulation in cells. Whereas P bodies are constitutively expressed and include … Continue reading
The function and dynamics of DMVs and CMs and the precise localization of the sites of active viral RNA synthesis are still unresolved questions, and further studies are required. A possible model proposes that DMVs may be the initial … Continue reading
In addition to DMVs, the gammacoronavirus IBV also induces different membrane structures such as spherules tethered to zippered endoplasmic reticulum. Unlike any previously identified coronavirus-induced structure, IBV spherules contain a pore connecting their interior to the cell cytoplasm.
The coexpression of the SARS-CoV transmembrane nonstructural proteins nsp3, nsp4 and nsp6 resulted in the formation of CMs and DMVs, suggesting a functionin the biogenesis of the membranous replicative structures, and also in the anchoring of the RTC.
In mouse hepatitis virus (MHV)-infected cells, newly synthesized RNA was detected in close proximity to DMVs and CMs, and viral RNA levels correlated with the number of DMVs. However, other data do not necessarily support the active contribution of … Continue reading
ROLE OF DOUBLE-MEMBRANE VESICLES Like that of other positive-strand RNA viruses, coronavirus RNA synthesis is associated with extensively rearranged intracellular membranes. High-resolution three-dimensional images obtained by electron tomography in SARS-CoV-infected cells showed a unique reticulovesicular network of modified endoplasmic … Continue reading
Alteration of coronavirus frame-shifting efficiency modified the ratio of replicase proteins, affecting viral RNA synthesis and virus production. In this sense, regulation of the ratio between the two vira lpolymerasess nsp8 and nsp12, encoded by ORF1a and ORF1b, respectively, … Continue reading
Corona proteins ratios are also posttranscriptionally regulated. Most sgmRNAs are structurally polycistronic but functionally monicistronic, with only the 5′-most ORF being translated into a viral protein. The clearest example of coronavirus translational regulation is the expression of the polyprotein … Continue reading
As components of the coronavirus RTC, cell proteins can also modulate sgmRNA ratios. Infectious bronchitis virus (IBV) N protein was recently shown to recruit cellular helicase DDX1 to viral RTCs, facilitating TRS read-through and synthesis of long sgmRNAs. Interestingly, DDX1 … Continue reading
Multiple factors regulate the transcription process by modulating the template switch frequency during discontinuous transcription. The most important one is the complementarity between the TRS-L and the cTRS-B. In a study of several coronaviruses, most sgmRNAs synthesized could be … Continue reading