| Mating pheromone pathway and cell wall integrity pathway are two crucial mitogen-activated protein kinase(MAPK) signal transduction pathways among the five MAPK pathways in the Saccharomyces cerevisiae. Very important crosstalks exist between these two pathways. Afr1 has a very important significant role in this crosstalk in that its expression is induced by Ste12 and Rlm1, which are the transcription factor of the mating pheromone pathway and the cell wall integrity pathway respectively. Structural characterization and functional analysis of Afr1p will shed new light on our current understanding about yeast.The main idea of this paper is about the function of AFR1 in cell cycle. Firstly,the strain 304(afr1Δ::LEU) had been constructed.Deletion of AFR1 delayed the recovery of cells fromα-factor arrest, indicating a functional role for Afr1p in promoting resumption of mitotic growth forα-factor-arrested G1 cells. Moreover,no clear effect was observed for a possible function of Afr1p in G0 cells to restart the mitotic cell cycle. afr1Δdelayed the recovery of cdc28-4 cells from arrest in restricted temperature, indicating a functional role for Afr1p in promoting resumption of mitotic growth for arrest cdc28-4(cdc28)cells.In Saccharomyces cerevisiae ,overexpression of Afr1p in mitotic cells resulted in overpolarized growth that lead to the formation of cells with elongated bud and multinuclear, a phenomenon similar with temperature sensitive septin mutants at restricted temperature. In order to prove that,the strain 915(HSL1-GFP) had been constructed. It was found that overexpression of AFR1 lead to Hsl1p cann't localize at the neck of bud in G2/M. Our results show that overexpression of AFR1 could destroy the function of Cdc12p ,and induce Hsl1p mislocalization .Thereby Hsl1p cann't phosphorylate Sew1p,resulting in cell arrest in G2/M. It was also found that afr1Δcann't affect Hsl1p localize at the neck of bud in G2/M.
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