IDENTIFICATION OF A GENE NECESSARY FOR CELL-CYCLE ARREST BY A NEGATIVE GROWTH-FACTOR OF YEAST - FAR1 IS AN INHIBITOR OF A G1 CYCLIN, CLN2

α factor is a negative growth factor and differentiation factor that induces G1 arrest and Increases transcription of mating genes in S. cerevislae a cells. We have Identified a gene, FAR1 (for "factor arrest"), which is necessary for cell cycle arrest but not for other responses to α factor: far1- mutants are insensitive to arrest despite having an intact signal transduction pathway. FAR1 is a nonessential gene whose expression is induced 4- to 5-fold in a cells by α factor. The sequence of FAR1 Indicates no significant similarities to known proteins. A null mutation in the CLN2 gene, which codes for a G1 cyclin, reverses the effect of a far1 null mutation: far1- cln2- strains arrest in response to α factor. We thus propose that FAR1 contributes to cell cycle arrest by inhibiting CLN2. The behavior of far1- cln2- strains indicates that products other than FAR1 are responsible for inhibiting the other G1 cyclins, CLN1 and CLN3. © 1990.