In yeast Saccharomyces cerevisiae, the Dhh1 protein, a member of the DEAD-box RNA helicase, stimulates Dcp2/Dcp1-mediated mRNA decapping and functions as a general translation repressor. Dhh1 also positively regulates translation of a selected set of mRNAs, including Ste12, a transcription factor for yeast mating and pseudohyphal growth. Given the diverse functions of Dhh1, we investigated whether the putative phosphorylation sites or the conserved motifs for the DEAD-box RNA helicases were crucial in the regulatory roles of Dhh1 during pseudohyphal growth. Mutations in the ATPase A or B motif (DHH1-K96R or DHH1-D195A) showed significant defects in pseudohyphal colony morphology and agar invasive phenotypes. The N-terminal phospho-mimetic mutation, DHH1-T16E, showed defects in pseudohyphal phenotypes. Decreased levels of Ste12 protein were also observed in these pseudohyphal-defective mutant cells under filamentous-inducing low nitrogen conditions. We suggest that the ATPase motifs and the Thr16 phosphorylation site of Dhh1 are crucial to its regulatory roles in pseudohyphal growth under low nitrogen conditions.

在酵母酿酒酵母中，Dhh1蛋白（DEAD-box RNA解旋酶的成员）刺激Dcp2 / Dcp1介导的mRNA脱盖并充当一般的翻译阻遏物。Dhh1还积极调节一组选定的mRNA的翻译，其中包括Ste12（酵母交配和假菌丝生长的转录因子）。考虑到Dhh1的各种功能，我们调查了DEAD-box RNA解旋酶的假定磷酸化位点或保守基序在假菌丝生长过程中对Dhh1的调控作用是否至关重要。ATPase A或B基序（DHH1- K96R或DHH1- D195A）中的突变在假菌丝菌落形态和琼脂浸润表型中显示出明显的缺陷。N-末端磷酸化模拟突变，DHH1- T16E，在假菌丝表型中显示出缺陷。在丝状诱导的低氮条件下，在这些假菌丝缺陷的突变细胞中还观察到Ste12蛋白的水平降低。我们建议ATP酶基序和Dhh1的Thr16磷酸化位点对于其在低氮条件下假菌丝生长中的调控作用至关重要。