XRN1 is a Species-Specific Virus Restriction Factor in Yeasts

In eukaryotes, the degradation of cellular mRNAs is accomplished by Xrn1p and the cytoplasmic exosome. Because viral RNAs often lack canonical caps or poly-A tails, they can also be vulnerable to degradation by these host exonucleases. Yeast lack sophisticated mechanisms of innate and adaptive immunity, but do use RNA degradation as an antiviral defense mechanism. One model is that the RNA of yeast viruses is subject to degradation simply as a side effect of the intrinsic exonuclease activity of proteins involved in RNA metabolism. Contrary to this model, we find a highly refined, species-specific relationship between Xrn1p and the \"L-A\" totiviruses of different Saccharomyces yeast species