Abstract

Dhh1 and Dhh1 homologues (RCK/p54/DDX6) are mem-bers of the DEAD-box protein family of RNA helicases. These proteins display conserved sequence motifs for ATPase and RNA binding activities. Dhh1 is a component of the P-bodies (processing bodies) of mRNA granules and functions as an mRNA decapping activator in Saccharomyces cerevisiae. Dhh1 also contributes to gene-specific regulation during yeast mating. The dhh1 deletion mutation results in a significant decrease in the expression of Ste12, a mating-specific trans-cription factor, showing severe mating defects. Here, we in-troduced amino-acid substitution mutations in the ATPase and RNA binding domains of Dhh1 and also constructed a deletion of 79 amino acids at the Q/P-rich C-terminal region. The mutations in ATPase A and B motif (K96R, D195A) and C-terminus deletion showed reduced levels of mating effi-ciency as well as Ste12 protein expression. The Q/P-rich C- terminal region of Dhh1 was dispensable for growth at non- permissive temperature 37°C but appeared to play an im-portant role in regulating the Ste12 protein expression and mating processes. The P-body accumulation induced by treatment with α-mating factor required ATPase, RNA-bind-ing and the Q/P-rich C-terminal domains of Dhh1.

• Keywords: RNA helicase; Dhh1; Ste12 expression; P-bodies; ATPase domain; Q/P-rich region