Common signal transduction system shared by STE2 and STE3 in haploid cells of Saccharomyces cerevisiae: autocrine cell-cycle arrest results from forced expression of STE2.
Induction of STE2 expression using the GAL1 promoter both in a wild-type MATalpha strain and in a MATalpha ste3 strain caused transient cell-cycle arrest and changes in morphology ('shmoo'-like phenotype) in a manner similar to alpha cells responding to alpha-factor. In addition, STE2 expressed in a MATalp[ha ste3 mutant allowed the cell to conjugate with alpha cells but at an efficiency lower than that of wil-type alpha cells. This result indicates that signal(s) generated by alpha-factor in alpha cells can be substituted by signal(s) generated by the interaction of alpha-factor with the expressed STE2 product. When STE2 or STE3 was expressed in a matalpha1 strain (insensitive to both alpha- and a-factors), the cell became sensitive to alpha- or a-factor, respectively, and resulted in morphological changes. These results suggest that STE2 and STE3 are the sole determinants for alpha-factor and a-factor sensitivity, respectively, in this strain. On the other hand, expression of STE2 in an a/alpha diploid cell did not affect the alpha-factor insensitive phenotype. Haploid-specific components may be necessary to transduce the alpha-factor signal. These results are consistent with the idea that STE2 encodes an alpha-factor receptor and STE3 encodes an a-factor receptor, and suggest that both alpha- and a-factors may generate an exchangeable signal(s) within haploid cells.
Department of Molecular Biology, DNAX Research Institute of Molecular and Cellular Biology, 901 California Avenue, Palo Alto, CA 94304, USA.
N
N
Nakayama
A
A
Miyajima
K
K
Arai
D002453:Cell Cycle / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal / Q000235:genetics; D006238:Haploidy; D010641:Phenotype; D010957:Plasmids / Q000235:genetics; D043562:Receptors, G-Protein-Coupled / Q000235:genetics*; D051964:Receptors, Mating Factor; D018000:Receptors, Peptide / Q000235:genetics*; D043563:Receptors, Pheromone / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*
D043562:Receptors, G-Protein-Coupled; D051964:Receptors, Mating Factor; D018000:Receptors, Peptide; D043563:Receptors, Pheromone; C081863:STE3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors