Genome-Wide Mapping of Decay Factor-mRNA Interactions in Yeast Identifies Nutrient Responsive Transcripts as Targets of the Deadenylase Ccr4

The Ccr4-Not complex is a major regulator of stress responses that controls gene expression at multiple levels, from transcription to mRNA decay. Ccr4, a core subunit of the complex, is the main cytoplasmic deadenylase in Saccharomyces cerevisiae, however its mRNA targets have not been mapped on a genome-wide scale. Here we describe a genome-wide approach, RNA immunoprecipitation-high throughput sequencing (RIP-seq), to identify the RNAs bound to Ccr4, and two proteins that associate with it, Dhh1 and Puf5. All three proteins were preferentially bound to lowly abundant mRNAs, most often at the 3' end of the transcript. Furthermore, Ccr4, Dhh1 and Puf5 are recruited to mRNAs that are targeted by other RNA-binding proteins that promote decay, mRNA transport and inhibit translation.  Although Ccr4-Not regulates mRNA transcription and decay, Ccr4 recruitment to mRNAs correlates better with decay rates, suggesting it imparts greater control over transcript abundance through decay.  Ccr4-enriched mRNAs are refractory to control by the other deadenylase complex in yeast, Pan2/3, suggesting a division of labor between these deadenylation complexes. Finally, Ccr4 and Dhh1 associate with mRNAs whose abundance increases during nutrient starvation and those that fluctuate during metabolic and oxygen consumption cycles, which explains the known genetic connections between these factors and nutrient utilization and stress pathways.

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