Implication of Ccr4-Not complex function in mRNA quality control in Saccharomyces cerevisiae.

Production of messenger ribonucleoprotein particles (mRNPs) is subjected to quality control (QC). In Saccharomyces cerevisiae, the RNA exosome and its cofactors are part of the nuclear QC machinery that removes, or stalls, aberrant molecules, thereby ensuring that only correctly formed mRNPs are exported to the cytoplasm. The Ccr4-Not complex, which constitutes the major S. cerevisiae cytoplasmic deadenylase, has recently been implied in nuclear exosome-related processes. Consistent with a possible nuclear function of the complex, the deletion or mutation of Ccr4-Not factors also elicits transcription phenotypes. Here we use genetic depletion of the Mft1p protein of the THO transcription/mRNP packaging complex as a model system to link the Ccr4-Not complex to nuclear mRNP QC. We reveal strong genetic interactions between alleles of the Ccr4-Not complex with both the exosomal RRP6 and MFT1 genes. Moreover, Rrp6p-dependent in vivo QC phenotypes of Δmft1 cells can be rescued by codeletion of several Ccr4-Not components. We discuss how the Ccr4-Not complex may connect with the mRNP QC pathway.