@article{mbs:/content/journal/jgv/10.1099/jgv.0.001386, author = "Neidel, Sarah and Torres, Alice A. and Ren, Hongwei and Smith, Geoffrey L.", title = "Leaky scanning translation generates a second A49 protein that contributes to vaccinia virus virulence", journal= "Journal of General Virology", year = "2020", volume = "101", number = "5", pages = "533-541", doi = "https://doi.org/10.1099/jgv.0.001386", url = "https://www.microbiologyresearch.org/content/journal/jgv/10.1099/jgv.0.001386", publisher = "Microbiology Society", issn = "1465-2099", type = "Journal Article", keywords = "leaky scanning", keywords = "vaccinia virus", keywords = "multiple functions", keywords = "virulence", keywords = "NF-κB inhibitor", keywords = "gene A49R", keywords = "Bcl2-fold", abstract = "Vaccinia virus (VACV) strain Western Reserve gene A49L encodes a small intracellular protein with a Bcl-2 fold that is expressed early during infection and has multiple functions. A49 co-precipitates with the E3 ubiquitin ligase β-TrCP and thereby prevents ubiquitylation and proteasomal degradation of IκBα, and consequently blocks activation of NF-κB. In a similar way, A49 stabilizes β-catenin, leading to activation of the wnt signalling pathway. However, a VACV strain expressing a mutant A49 that neither co-precipitates with β-TrCP nor inhibits NF-κB activation, is more virulent than a virus lacking A49, indicating that A49 has another function that also contributes to virulence. Here we demonstrate that gene A49L encodes a second, smaller polypeptide that is expressed via leaky scanning translation from methionine 20 and is unable to block NF-κB activation. Viruses engineered to express either only the large protein or only the small A49 protein both have lower virulence than wild-type virus and greater virulence than an A49L deletion mutant. This demonstrates that the small protein contributes to virulence by an unknown mechanism that is independent of NF-κB inhibition. Despite having a large genome with about 200 genes, this study illustrates how VACV makes efficient use of its coding potential and from gene A49L expresses a protein with multiple functions and multiple proteins with different functions.", }