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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
Author(s) -
Zähringer Harald,
Thevelein Johan M.,
Nwaka Solomon
Publication year - 2000
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2000.01706.x
Subject(s) - biology , trehalase , activator (genetics) , biochemistry , osmotic shock , trehalose , mutant , transcription factor , saccharomyces cerevisiae , gene
Saccharomyces cerevisiae neutral trehalase, encoded by NTH1, controls trehalose hydrolysis in response to multiple stress conditions, including nutrient limitation. The presence of three st ress r esponsive e lements (STREs, CCCCT) in the NTH1 promoter suggested that the transcriptional activator proteins Msn2 and Msn4, as well as the cAMP‐dependent protein kinase (PKA), control the stress‐induced expression of Nth1 . Here, we give direct evidence that Msn2/Msn4 and the STREs control the heat‐, osmotic stress‐ and diauxic shift‐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%. The trehalose concentration in the msn2 msn4 double mutant increases less during heat stress and drops more slowly during recovery than in wild‐type cells. This shows that Msn2/Msn4‐controlled expression of enzymes of trehalose synthesis and hydrolysis help to maintain trehalose concentration during stress. However, the Msn2/Msn4‐independent mechanism exists for heat control of trehalose metabolism. Site‐directed mutagenesis of the three STREs (CCCCT changed to CATCT) in NTH1 promoter fused to a reporter gene indicates that the relative proximity of STREs to each other is important for the function of NTH1 . Elimination of the three STREs abolishes the stress‐induced responses and reduces basal expression by 30%. Contrary to most STRE‐regulated genes, the PKA effect on the induction of NTH1 by heat and sodium chloride is variable. During diauxic growth, NTH1 promoter‐controlled reporter activity strongly increases, as opposed to the previously observed decrease in Nth1 activity, suggesting a tight but opposite control of the enzyme at the transcriptional and post‐translational levels. Apparently, inactive trehalase is accumulated concomitant with the accumulation of trehalose. These results might help to elucidate the general connection between control by STREs, Msn2/Msn4 and PKA and, in particular, how these components play a role in control of trehalose metabolism.