User:Immcarle194/Interferon-stimulated gene

Interferon-stimulated gene
It's currently estimated that 10% of the human genome is regulated by interferons (INFs). Interferon stimulated genes can act as an initial response to pathogen invasion, slowing down viral replication and increasing expression of immune signaling complexes. There are three known types of interferon. With approximately 450 genes highly expressed in response to interferon type I. Type I interferon consists of INF-α, INF-β, INF-ω and is expressed in response to viral infection. ISGs induced by type I interferon are associated with viral replication suppression and increase expression of immune signaling proteins. Type II interferon consists only of INF-γ and is associated with controlling intracellular pathogens and tumor suppressor genes. Type III interferon consists of INF-λ and is associated with viral immune response and is key in anti-fungal neutrophil response.

IFIT Family of Interferon stimulated genes
The IFIT family of ISGs is located on chromosome 10 in humans and is homologous in mammals, birds, and fish. The IFIT family is commonly induced by type I and type III interferon. IFIT gene expression has been observed in response to both DNA and RNA viral infection. IFIT genes suppress viral infection primarily by limiting viral RNA and DNA replication. IFIT proteins 1,2,3 and 5 can bind directly to double-stranded triphosphate RNA. These IFIT proteins form a complex that destroys the viral RNA. IFIT 1 and IFIT 2 directly bind Eukaryotic initiation factor 3,  which reduces more then 60% of protein translation in the targeted cell.

Function
As such a large portion of the human genome is associated with interferon ISG have a broad range of functions. ISG are essential for fighting off viral bacterial and parasitic pathogens. Interferon stimulates genes that help active immune response and suppress infection at almost all stages of infection.

inhibition of viral RNA
There are 21 know ISG that inhibit RNA virus replication. Primarily ISG bind to and degrade RNA to prevent viral instructions from being translated into viral proteins. These ISG can specifically target double stranded triphosphate RNA which is distinct from single stranded RNA present in human cells. ISG can also non specifically target mRNA and destroy it. Cell wide mRNA degradation prevents both viral gene translation and regular proteins from being produced. INF-α and other key immune proteins mRNA is resistant to this cell wide degradation to allow immune signals to continue while protein. translation is inhibited to prevent infection.

Apoptotic effects
there are 15 known ISG that help induce apoptosis. It is likely that none of these genes trigger apoptosis alone but their expression has been linked to apoptosis. Higher expression of ISG make the cell more susceptible to natural killer cells.