imaging and histology
Recorded terms: confocal immunofluorescence; immunofluorescence; immunofluorescence confocal microscopy; immunofluorescence microscopy; immunofluorescence microscopy and colocalization analysis
The Capicua and ATXN1L repressor complex binds an eight-nucleotide motif at interferon and interferon-stimulated gene loci to hold them repressed during homeostasis in human and mouse cells, and is degraded through EGFR-MAPK signaling early in respiratory viral entry, which relieves that repression.
In golden hamsters, productive SARS-CoV-2 replication in the airways generates circulating type I and III interferon that primes every organ against infection, and blunting or bypassing that airway response permits viremia and productive infection of liver, kidney, spleen and brain.
Stress granules restrain rather than amplify double-stranded RNA sensing, and cells lacking the granule nucleators G3BP1 and G3BP2, UBAP2L or PKR respond to double-stranded RNA with excessive RIG-I-like receptor, PKR and OAS activation and MAVS-dependent apoptosis.
Kinase substrate specificity profiling assigns the phosphorylation cluster in the SARS-CoV-2 nucleocapsid SR-rich domain to a cascade initiated by SRPK1 and SRPK2 and extended by GSK-3 and casein kinase 1, whose inhibition suppresses coronavirus replication.
SARS-CoV-2 infection of the olfactory epithelium reorganizes the nuclear architecture of uninfected olfactory sensory neurons, dissipating the interchromosomal compartments that hold olfactory receptor genes and suppressing receptor and signal transduction transcription in both hamsters and human autopsy tissue.
A microfluidic bronchial airway chip lined with differentiated human airway epithelium and pulmonary endothelium reproduces strain-dependent influenza virulence, cytokine output and neutrophil recruitment, and when drugs are delivered at clinically achievable blood concentrations under flow it separates candidates that work in cell lines from those that also work in hamsters challenged with SARS-CoV-2.
A genome-scale CRISPR loss-of-function screen in ACE2-expressing human alveolar epithelial cells ranks every protein-coding gene by the effect of its loss on SARS-CoV-2 infection, converging on endosomal machinery, and links several top hits to increased cholesterol biosynthesis and, for RAB7A, to intracellular sequestration of ACE2.
Human ocular surface tissue carries SARS-CoV-2 entry machinery and supports productive replication, with the limbus most permissive in both adult donor cells and stem cell derived whole-eye cultures, where infection drives NF-kB chemokine induction and blunted interferon signaling.
SARS-CoV-2 infection of human lung epithelial cells engages NF-κB at chromatin, transcriptional, protein and post-translational levels without engaging the type I interferon transcription factors, and loss of p65 or p50 abolishes viral replication in a manner rescued by reconstituting RelA transcriptional activity.
A panel of eight human pluripotent stem cell derivatives spanning all three germ layers, together with adult primary islets and liver organoids, identifies pancreatic alpha and beta cells, hepatocytes, cholangiocytes, cardiomyocytes and dopaminergic neurons as permissive to SARS-CoV-2 and shows that permissiveness does not track ACE2 expression alone.
A time-resolved phosphoproteomic survey of SARS-CoV-2-infected cells showing that infection acts mainly through signalling rather than protein abundance, activating casein kinase II and the p38 cascade while shutting down mitotic kinases, and converting that kinase profile into inhibitors with antiviral activity.
Applying one uniform small RNA-based selective pressure to four virus families in vertebrate cells shows that the ability to escape it tracks with the capacity for polymerase template switching rather than with genome polarity as such, since positive-strand viruses excise the targeted sequence while negative-strand viruses are cleared and a recombination-defective poliovirus cannot escape.
Loss of the nuclear RNase III enzyme Drosha, but not of Dicer, increases RNA virus replication in mammalian fibroblasts, and diverse RNA viruses drive Drosha into the cytoplasm by CRM1-dependent export in a manner that does not require new protein synthesis, RIG-I, TBK1 or type I interferon signaling.
Sustained IRF7 activity induces the kinase MAP3K8, which phosphorylates the proline-rich hinge of IRF3 and redirects it from homodimers into IRF3 and IRF7 heterodimers, broadening the antiviral transcriptome and scaling the cellular response to the persistence of the viral threat.
The inefficient 5 prime splice site of influenza A virus segment 8 functions as a timing device, causing the nuclear export protein to accumulate slowly as a minor product of abundant NS1 transcription, with both raising and lowering that rate attenuating the virus through mistimed ribonucleoprotein export.
Primary microRNA transcripts generated in the cytoplasm by a recombinant Sindbis virus are cleaved without any nuclear involvement yet still require Drosha, which relocalises from nucleus to cytoplasm on infection while the endogenous microRNA profile of the cell remains largely unchanged.
Influenza A virus can be engineered to encode a cellular pri-microRNA inside an artificial intron of segment 8 and to produce mature, silencing-competent miR-124 during infection without measurable loss of replication or genome stability.
Insertion of a primary microRNA locus into the exclusively cytoplasmic Sindbis virus genome yields mature, functional miR-124 through a Dicer-dependent but microprocessor- and Exportin-5-independent route, defining a cytoplasmic hairpin-processing activity in vertebrate cells that the authors term a virtron.