Flocculation in Saccharomyces cerevisiae is regulated by RNA/DNA helicase Sen1p

The Nrd1-Nab3-Sen1 (NNS) complex terminates transcription of non-coding RNA genes and mediates degradation of the produced transcript by the nuclear exosome. The NNS complex also represses some stress response genes, by stimulating premature termination. A well-characterized stress response in yeast is flocculation, where cells aggregate to form flocs under expression of lectin-encoding genes designated as FLOs. In this study, we demonstrated the role of the NNS complex and Rrp6p in the expression of flocculation genes: FLO1, FLO5, FLO9, and FLO10. Furthermore, a deletion mutant of the RNA processing machinery (RNT1), and SEN1 mutants that are unable to interact with Rnt1p, exhibit a flocculation phenotype. In summary, we have identified a cooperative role of Rnt1p, Rrp6p and the NNS complex in the repression of FLO genes.