Induction of neutral trehalase Nth1 by heat and osmotic stress is controlled by STRE elements and Msn2/Msn4 transcription factors: variations of PKA effect during stress and growth

Saccharomyces cerevisiae neutral trehalase, encoded by NTH1, controls treha lose hydrolysis in response to multiple stress conditions, including nutrie nt limitation. The presence of three stress responsive elements (STREs, CCC CT) in the NTH1 promoter suggested that the transcriptional activator prote ins Msn2 and Msn4, as well as the cAMP-dependent protein kinase (PKA), cont rol the stress-induced expression of Nth1. Here, we give direct evidence th at Msn2/Msn4 and the STREs control the heat-, osmotic stress- and diauxic s hift-dependent induction of Nth1, Disruption of MSN2 and MSN4 abolishes or significantly reduces the heat- and NaCl-induced increases in Nth1 activity and transcription. Stress-induced increases in activity of a lacZ reporter gene put under control of the NTH1 promoter is nearly absent in the double mutant. In all instances, basal expression is also reduced by about 50%, T he trehalose concentration in the msn2 msn4 double mutant increases less du ring heat stress and drops more slowly during recovery than in wildtype cel ls. This shows that Msn2/Msn4-controlled expression of enzymes of trehalose synthesis and hydrolysis help to maintain trehalose concentration during s tress. However, the Msn2/Msn4-independent mechanism exists for heat control of trehalose metabolism. Site-directed mutagenesis of the three STREs (CCC CT changed to CATCT) in NTH1 promoter fused to a reporter gene indicates th at the relative proximity of STREs to each other is important for the funct ion of NTH1, Elimination of the three STREs abolishes the stress-induced re sponses and reduces basal expression by 30%, Contrary to most STRE-regulate d genes, the PKA effect on the induction of NTH1 by heat and sodium chlorid e is variable. During diauxic growth, NTH1 promoter-controlled reporter act ivity strongly increases, as opposed to the previously observed decrease in Nth1 activity, suggesting a tight but opposite control of the enzyme at th e transcriptional and post-translational levels. Apparently, inactive treha lase is accumulated concomitant with the accumulation of trehalose. These r esults might help to elucidate the general connection between control by ST REs, Msn2/Msn4 and PKA and, in particular, how these components play a role in control of trehalose metabolism.