Lre1 affects chitinase expression, trehalose accumulation and heat resistance through inhibition of the Cbk1 protein kinase in Saccharomyces cerevisiae

Versele, M Thevelein, JM

M. Versele et Jm. Thevelein, Lre1 affects chitinase expression, trehalose accumulation and heat resistance through inhibition of the Cbk1 protein kinase in Saccharomyces cerevisiae, MOL MICROB, 41(6), 2001, pp. 1311-1326

57

INGLESE

Article

Microbiology

MOLECULAR MICROBIOLOGY

0950-382X → ACNP

41

6

2001

1311 - 1326

ISI

0950-382X(200109)41:6<1311:LACETA>2.0.ZU;2-T

The addition of glucose to derepressed cells of the yeast Saccharomyces cer evisiae triggers activation of the cAMP pathway with a rapid drop in stress resistance as a consequence. We have isolated the LRE1 gene as a multicopy suppressor of glucose-induced loss of heat resistance. Overexpression of L RE1 in a wild-type strain causes the same phenotype as observed in strains with reduced activity of the cAMP-PKA pathway: higher heat resistance and e nhanced trehalose levels. Deletion of LRE1 results in the opposite phenotyp es. Epistasis analysis indicates that these effects are independent of cAMP and PKA, of the protein kinases Yak1, Sch9 and Rim15 and of the transcript ion factors Msn2 and Msn4. Lre1 has recently been isolated in a two-hybrid screen using the conserved protein kinase Cbk1 as a bait. Cbk1 controls the expression of CTS1 (encoding chitinase) through the transcription factor A ce2. We demonstrate here that overexpression of LRE1 represses CTS1 whereas deletion of LRE1 induces the expression of CTS1. Repression of CTS1 result s in deficient cell separation as a result of inefficient degradation of th e chitin ring after cytokinesis. Neither deletion nor overexpression of LRE 1 has any effect on CTS1 expression in a cbk1 Delta mutant, indicating that Lre1 inhibits Cbk1. In addition, we show that increased trehalose accumula tion and increased heat resistance caused by overexpression of LRE1 are als o the result of inhibition of Cbk1, revealing a novel control pathway for c ertain targets affected by PKA. The yeast genome contains a homologue of LR E1, YDR528w, which we have called HLR1 (for homologue of Lre1). Deletion an d overexpression of HLR1 causes similar but less pronounced effects compare d with LRE1.