The ubiquitin ligase SCFGrrl is necessary for pheromone sensitivity in Saccharomyces cerevisiae

The presence of the appropriate pheromone induces a and a cells of the yeast Saccharomyces cerevisiae to activate both changes in transcriptional expression and cell polarity that eventually lead to the mating of et and a cells to form a/alpha diploid cells. A third response after exposure to mating pheromone is a transient cell cycle arrest, allowing synchronization of the two cell types in G(1) prior to cell fusion. At least in part, this cell cycle arrest requires the inactivation of Cln-kinase activity through transcriptional inactivation of the CLN1 and CLN2 genes, degradation of the On proteins and direct inhibition of Cln-kinase complexes. Here we report that GRR1, which encodes a substrate recognition subunit of SCF complexes, is critical for pheromone sensitivity and likely for this arrest. Loss of SCFGrr1 function by deletion of the GRR1 gene causes pheromone resistance. However, deletion of CLN1 and CLN2 restores pheromone sensitivity to grr1 Delta cells. Thus, rapid loss of Cln-kinase activity during mating may require coordinated inactivation of the Cln-kinase complexes, inactivation of CLN transcription and SCFGrr1-dependent On degradation. Copyright (c) 2005 John Wiley & Sons, Ltd.