Utilization of nonfermentable carbon resources by and requires the Snf1p kinase and the Cat8p transcriptional activator, which binds to carbon source-responsive components of focus on genes. noticed. A serine-to-glutamate mutant type mimicking constitutive phosphorylation outcomes in a almost constitutively active type of KlCat8p, while a serine-to-alanine mutation gets the reverse impact. Furthermore, it really is demonstrated that KlCat8p phosphorylation depends upon strengthens the hypothesis of immediate phosphorylation of Cat8p by Snf1p. Unlike that of transcription isn’t carbon resource regulated, illustrating the prominent part of posttranscriptional regulation of Cat8p in and show a higher amount of sequence conservation, and the genes encoding their regulators, although showing much less sequence similarity, are generally with the capacity of heterospecific complementation aswell (38). The molecular bases for the physiological variations between and so are right now known: in and a good example of such a differential construction, explaining the dissimilar development properties of both yeasts. In (encoding fructose-1,6-bisphosphatase) (10, 23, 35) or (encoding phosphoenolpyruvate carboxykinase) (23, 26) and glyoxylate routine genes like (encoding malate synthase) (5), (encoding isocitrate lyase) (18, 31), and (encoding acetyl coenzyme A synthase) (19). Two CSRE-binding elements influencing the transcription of gluconeogenic genes have already been identified: Cat8p (27) and Sip4p (34). Both proteins are members of the Zn(II)2Cys6 zinc cluster family, and their activity is dependent on a functional Snf1p protein (17, 34), the central kinase purchase TAE684 required for growth on alternative sugars and nonfermentable carbon sources such as sucrose, glycerol, and ethanol (4, 6, 40). Whereas two-hybrid interaction revealed Sip4p as a direct phosphorylated target of the Snf1p kinase (21), a direct interaction between Cat8p and Snf1p could not be demonstrated (36). However, genetic evidence supports this hypothesis (17). Functional homologues of Snf1p and Cat8p have been identified in complemented the phenotype of the mutant (deficient in fermentative and oxidative growth) and shows high sequence similarity to (14). was cloned by high-copy suppression of the mutation, suggesting that it acts downstream of KlSnf1p (13). A mutation revealed that KlCat8p is required MAPK3 for efficient utilization of C2 carbon sources like ethanol or acetate but is dispensable for growth on glycerol and for derepression of and (13). To elucidate the signaling events leading to activation of Cat8p, we assayed for two-hybrid interaction between KlSnf1p and KlCat8p. Our data support the view that KlCat8p is a direct target of KlSnf1p kinase activity. Serine 661, located in an Snf1 consensus phosphorylation site, was identified as a regulatory site that controls the KlCat8p activation function, probably via regulated phosphorylation, and corresponding serine 562 in ScCat8p has a similar role. MATERIALS AND METHODS Strains, media, and yeast techniques. strain DH10B (Gibco BRL) was used for all cloning procedures and was grown on standard Luria-Bertani medium. strain BOY (strain MAV103 (strains CEN.NB1-1A (strains used in this study were JA6 (wild-type purchase TAE684 allele. The first step was purchase TAE684 carried out by site-specific integration, in JA6, of the pRS306-CAT8S661A and pRS306-CAT8S661E vectors linearized within the open reading frame (ORF) by digestion with BlpI. In the second step, eviction of the integrated plasmid was obtained by selection for loss of the vector’s marker on minimal medium supplemented with 5-fluoroorotic acid. Replacement of the wild-type allele with the mutated S661A or S661E allele of KlCat8p was verified among 5-fluoroorotic acid-resistant clones by sequencing of PCR-amplified chromosomal DNA and Southern blot analysis. All yeasts were grown in minimal medium (0.67% Difco yeast nitrogen base without amino acids supplemented with the required amino acids and bases) containing the appropriate carbon source. Plasmids. KlCAT8 was amplified from genomic DNA with primers uCAT8 (5-TGCTCTAGAATGGTCGAGAAGAAAGAT-3) and dCAT8 (5-ATAGTTTAGCGGCCGCTCAATTTCCATTTTGCCAGCG-3), adding XbaI and NotI restriction sites to the 5 and 3 ends of the ORF, respectively. The PCR fragment was cloned in XbaI/NotI sites of pRS306, pJG45 (15), and pEG202 (15) to give pRS306CAT8, pJG45CAT8, and pEG202CAT8, respectively. pEG202CAT83204-4335 was obtained by BamHI/NotI restriction of pEG202CAT8, Klenow polymerase fill in, and self-ligation. pGBT9KlCAT8 was constructed by inserting an XbaI/SalI fragment of pEG202CAT8 and an EcoRI/XbaI linker (5-GAATTCCCGGGGATCCGTCGAC-3) into the multiple cloning site of pGBT9 (Clontech). pEG202CAT848-3405 and pGBT9KlCAT848-3405 were obtained by NcoI restriction of pEG202CAT8 and pGBT9KlCAT8, respectively, and.