Mechanisms of VTS1-Mediated Repression in Saccharomyces Cerevisiae

Book excerpt: Vts1p is the Saccharomyces cerevisiae member of the Smaug family of post-transcriptional regulators, which is a group of sequence-specific RNA-binding proteins that regulate target mRNA expression. Vts1p is known to mediate deadenylation-dependent degradation of target transcripts through the recruitment of the Ccr4p/Pop2p/Not deadenylase complex. By conducting a functional analysis of Vts1p deletion mutants, I demonstrate that two regions within Vts1p are independently capable of downregulating the expression of an mRNA reporter. I provide both genetic and biochemical evidence that suggests residues 170-523 regulate reporter expression at the level of mRNA stability and function through a mechanism that requires the Ccr4p/Pop2p/Not deadenylase, whereas residues 1-237 repress reporter expression at the level of translation and function through a novel mechanism. In addition, I map a direct interaction between the eIF4E-binding protein, Eap1p, and the Vts1p SAM domain, which suggests a model in which residues 170-523 recruit Eap1p to mediate efficient target transcript degradation.