Conservation of mRNA quality control factor Ski7 and its diversification through changes in alternative splicing and gene duplication

Significance The rapid degradation of mRNAs that lack a stop codon is critical to fidelity of gene expression and in yeast, it requires Ski7. Ski7 function is not fully understood andSKI7 -like genes are not apparent in other organisms. We show that in most eukaryotes Ski7 is expressed as an alternative splice isoform from theHBS1 gene. This most conserved example of alternative splicing probably arose in the common ancestor of animals, fungi, and plants. However, in six taxa alternative splicing was replaced by duplicated genes. After each duplication theSKI7 -like gene has undergone several changes that we analyzed experimentally. The results clarify how duplicated genes diversify, identify novelSKI7 -like genes, and reveal changes in nonstop mRNA decay.