Cellular glycan modification by B3GAT1 broadly restricts influenza virus infection.

Communicable respiratory viral infections pose both epidemic and pandemic threats and broad-spectrum antiviral strategies could improve preparedness for these events. To discover host antiviral restriction factors that may act as suitable targets for the development of host-directed antiviral therapies, we here conduct a whole-genome CRISPR activation screen with influenza B virus (IBV). A top hit from our screen, beta-1,3-glucuronyltransferase 1 (B3GAT1), effectively blocks IBV infection.

Host protein kinases required for SARS-CoV-2 nucleocapsid phosphorylation and viral replication.

Multiple coronaviruses have emerged independently in the past 20 years that cause lethal human diseases. Although vaccine development targeting these viruses has been accelerated substantially, there remain patients requiring treatment who cannot be vaccinated or who experience breakthrough infections. Understanding the common host factors necessary for the life cycles of coronaviruses may reveal conserved therapeutic targets.

A Virion-Based Combination Vaccine Protects against Influenza and SARS-CoV-2 Disease in Mice.

Vaccines targeting SARS-CoV-2 have been shown to be highly effective; however, the breadth against emerging variants and the longevity of protection remains unclear. Postimmunization boosting has been shown to be beneficial for disease protection, and as new variants continue to emerge, periodic (and perhaps annual) vaccination will likely be recommended. New seasonal influenza virus vaccines currently need to be developed every year due to continual antigenic drift, an undertaking made possible by a robust global vaccine production and distribution infrastructure.

Influenza A virus segments five and six can harbor artificial introns allowing expanded coding capacity.

Influenza A viruses encode their genomes across eight, negative sense RNA segments. The six largest segments produce mRNA transcripts that do not generally splice; however, the two smallest segments are actively spliced to produce the essential viral proteins NEP and M2. Thus, viral utilization of RNA splicing effectively expands the viral coding capacity without increasing the number of genomic segments.

ETV7 limits antiviral gene expression and control of influenza viruses.

The type I interferon (IFN) response is an important component of the innate immune response to viral infection. Precise control of IFN responses is critical because insufficient expression of IFN-stimulated genes (ISGs) can lead to a failure to restrict viral spread, whereas excessive ISG activation can result in IFN-related pathologies. Although both positive and negative regulatory factors control the magnitude and duration of IFN signaling, it is also appreciated that several ISGs regulate aspects of the IFN response themselves.

The FDA-approved drug Alectinib compromises SARS-CoV-2 nucleocapsid phosphorylation and inhibits viral infection in vitro.

While vaccines are vital for preventing COVID-19 infections, it is critical to develop new therapies to treat patients who become infected. Pharmacological targeting of a host factor required for viral replication can suppress viral spread with a low probability of viral mutation leading to resistance. In particular, host kinases are highly druggable targets and a number of conserved coronavirus proteins, notably the nucleoprotein (N), require phosphorylation for full functionality.

Promoter Pull-Down Assay: A Biochemical Screen for DNA-Binding Proteins.

Transcription factors are ubiquitous proteins that associate with promoter DNA and regulate gene expression through a variety of mechanisms. Understanding transcriptional control mechanisms requires in-depth investigation of the binding of transcription factors to the promoters they regulate. There are many in vivo and in vitro methods for testing the binding of a known protein to a promoter, such as chromatin immunoprecipitation and electrophoretic mobility shift assays.

Hierarchical Transcriptional Control of the LuxR Quorum-Sensing Regulon of Vibrio harveyi.

In vibrios, quorum sensing controls hundreds of genes that are required for cell density-specific behaviors including bioluminescence, biofilm formation, competence, secretion, and swarming motility. The central transcription factor in the quorum-sensing pathway is LuxR/HapR, which directly regulates ∼100 genes in the >400-gene regulon of Among these directly controlled genes are 15 transcription factors, which we predicted would comprise the second tier in the hierarchy of the LuxR regulon. We confirmed that LuxR binds to the promoters of these genes and quantified the extent of LuxR activation or repression of transcript levels.

Global H-NS counter-silencing by LuxR activates quorum sensing gene expression.

Bacteria coordinate cellular behaviors using a cell-cell communication system termed quorum sensing. In Vibrio harveyi, the master quorum sensing transcription factor LuxR directly regulates >100 genes in response to changes in population density. Here, we show that LuxR derepresses quorum sensing loci by competing with H-NS, a global transcriptional repressor that oligomerizes on DNA to form filaments and bridges.

Quorum Sensing Gene Regulation by LuxR/HapR Master Regulators in Vibrios.

The coordination of group behaviors in bacteria is accomplished via the cell-cell signaling process called quorum sensing. Vibrios have historically been models for studying bacterial communication due to the diverse and remarkable behaviors controlled by quorum sensing in these bacteria, including bioluminescence, type III and type VI secretion, biofilm formation, and motility. Here, we discuss the LuxR/HapR family of proteins, the master global transcription factors that direct downstream gene expression in response to changes in cell density.

Integration host factor and LuxR synergistically bind DNA to coactivate quorum-sensing genes in Vibrio harveyi.

The cell-cell signaling process called quorum sensing allows bacteria to control behaviors in response to changes in population density. In Vibrio harveyi, the master quorum-sensing transcription factor LuxR is a member of the TetR family of transcription factors that both activates and represses genes to coordinate group behaviors, including bioluminescence. Here, we show that integration host factor (IHF) is a key coactivator of the luxCDABE bioluminescence genes that is required together with LuxR for precise timing and expression levels of bioluminescence during quorum sensing.