探討酵母菌核醣核酸蛋白Rbp1p對絲狀生長之調控

Abstract

The RNA binding protein, Rbp1p, was first identified as a negative regulator in Saccharomyces cerevisiae. RBP1 encodes a 672-amino acid, ~80-kD protein, which contains three RNA recognition motifs (RRM), two glutamine-rich stretches, and one asparagine-methionine-proline-rich (NMP-rich) region. Our lab previously has showed that overexpression Rbp1p RRM mutants in BY4741 induced agar-adhesion, a typical phenotype of yeast filamentous growth. In this study, we asked whether endogenous Rbp1p plays a role in filamentous growth of Σ1278b strain. Here we showed that deletion of RBP1 enhances agar adhesion, invasion and cell elongation. These phenotypes induced by rbp1 mutation depend on FLO11, which encodes a cell-wall glycoprotein regulating filamentous growth. The flo11 rbp1 double mutant fails to adhere to agar. Deletion of RBP1 significantly activates the FLO11 mRNA level, suggesting that Rbp1p negatively regulates filamentous growth through inhibition of FLO11 mRNA expression. The RRM2 motif and NMP-rich region are important for its adhesive phenotypes. Both transcription factors in MAPK pathway, Ste12p and cAMP-PKA pathway, Flo8p are required for rbp1-induced hyper-agar adhesion and FLO11 activation. Sfl1p, another transcription factor in cAMP-PKA pathway, which represses FLO11 transcripts. The FLO11 mRNA level in rbp1 sfl1 double mutant was increased much more than sfl1 mutant, implying that Rbp1p may regulate FLO11 expression in parallel with Sfl1p. Dhh1p, one of Rbp1p interacting proteins, might participate in Rbp1p-mediated adhesive growth. However, the exact mechanism for Rbp1p to regulate FLO11 expression still remains to be investigated.