Suppression of the effects of an spt10 mutation on ADH2 expression is a phenotype shared by a small number of genes involved in the regulation of gene expression. All six known suppressors of spt10 are either components of the CCR4-NOT Complex (CCR4, CAF1, NOT4), or have been shown to interact with the complex ( DBF2, SRB9, SRB10). This indicated that spt10 suppression may be characteristic of CCR4-like gene regulation. In this work, I conducted a screen for additional suppressors of spt10 at ADH2. The screen identified no less than ten complementation groups, including ADH2 and two known suppressors of spt10, CCR4 and CAF1. Further analysis identified three previously unidentified suppressors of spt10, ASG2/ EBS1, ASG3/LSM6, and ASG6/ NUP159. Each of these genes is proposed to affect ADH2 expression at a step subsequent to transcriptional initiation, namely mRNA degradation. Along with the recent identification of CCR4 and CAF1 as key components of the major yeast deadenylase, this research shows that there are important regulatory factors at multiple points of mRNA degradation which are important for understanding the complete regulation of ADH2 expression and overall gene expression.
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