Dual Influence of the Yeast Catlp (Snflp) Protein Kinase on Carbon Source-Dependent Transcriptional Activation of Gluconeogenic Genes by the Regulatory Gene CAT8

Abstract

The CSRE (carbon source-responsive element) is a sequence motif responsible for the transcriptional activation of gluconeogenic structural genes in Saccharomyces cerevisiae. We have isolated a regulatory gene, DIL1 (derepression of isocitrate lyase, = CAT8), which is specifically required for derepression of CSRE-dependent genes. Expression of CAT8 is carbon source regulated and requires a functional Cat1p (Snf1p) protein kinase. The derepression defect of CAT8 in a cat1 mutant could be suppressed by a mutant Mig1p repressor protein. Derepression of CAT8 also requires a functional HAP2 gene, suggesting a regulatory connection between respiratory and gluconeogenic genes. Carbon source-dependent protein-CSRE complexes detected in a gel retardation analysis with wild-type extracts were absent in cat8 mutant extracts. However, similar experiments with an epitope-tagged CAT8 gene product in the presence of tag-specific antibodies gave evidence against a direct binding of Cat8p to the CSRE. A constitutively expressed GAL4-CAT8 fusion gene revealed a carbon source-dependent transcriptional activation of a UAS(GAL)-containing reporter gene. Activation mediated by Cat8p was no longer detectable in a cat1 mutant. Thus, biosynthetic control of CAT8 as well as transcriptional activation by Cat8p requires a functional Cat1p protein kinase. A model proposing CAT8 as a specific activator of a transcription factor(s) binding to the CSRE is discussed.

Ubp8 and SAGA Regulate Snf1 AMP Kinase Activity

“…While it is involved in a wide variety of cellular processes, its major function in yeast is to induce expression of glucose-repressed genes when cells are grown on nonfermentable carbon sources through phosphorylationmediated activation and deactivation of transcriptional regulators (28). To confirm the results of our biochemical screen, we purified 6ϫHis-myc-ubiquitin from wild-type and ubp8⌬ strains expressing a tandem affinity purification (TAP)-tagged version of Snf1 and a 6ϫHis-myc epitope-tagged ubiquitin construct.…”

“…One highly conserved mechanism involves the phosphorylation of the T loop at threonine 210 (T210) (14,19,24,36), which closely parallels the activation of Snf1 and many other AMP kinases. When yeast cells grown in glucose are switched to less-preferred carbon sources, Snf1 becomes phosphorylated and then activates the expression of genes involved in utilization of these carbon sources by regulating the activity of downstream transcriptional modulators (12,20,28,29,33,39). Interestingly, hyperubiquitination of mammalian Snf1-related AMP-activated protein kinases is associated with a marked decrease in T-loop phosphorylation, suggesting that ubiquitination regulates their activity (1).…”

Life in the midst of scarcity: adaptations to nutrient availability in Saccharomyces cerevisiae

“…Dashed lines represent putative or indirect interactions. See text for further details Mig1-dependent repression under high-glucose conditions (Hedges et al 1995), and once synthesized upon glucose exhaustion, the protein must first be phosphorylated by Snf1 to obtain its transcriptional activity (Rahner et al 1996;Randez-Gil et al 1997). Cat8 induces transcription of SIP4 (Vincent and Carlson 1998), and subsequent Snf1-dependent phosphorylation of Sip4 then leads to proper induction of gluconeogenic genes by both Cat8 and Sip4 (Hiesinger et al 2001).…”

Adr1 and Cat8 synergistically activate the glucose-regulated alcohol dehydrogenase gene ADH2 of the yeast Saccharomyces cerevisiae

“…This led to the identification of a common cis-acting element, designated CSRE (carbon source-responsive element ; consensus CCRTYSRNCCG ; reviewed by Entian & Schu$ ller, 1997 ;Gancedo, 1998), which could confer glucose-sensitive gene regulation to a synthetic minimal promoter. CSRE-dependent gene activation requires a functional CAT8 gene (Hedges et al, 1995 ;Rahner et al, 1996), encoding a transcription factor with a binuclear zinc cluster domain at its N terminus and a Cterminal transcription activation domain. Expression of CAT8, as well as transcription activation by Cat8, is affected by carbon source (Rahner et al, 1996 ;RandezGil et al, 1997).…”

“…CSRE-dependent gene activation requires a functional CAT8 gene (Hedges et al, 1995 ;Rahner et al, 1996), encoding a transcription factor with a binuclear zinc cluster domain at its N terminus and a Cterminal transcription activation domain. Expression of CAT8, as well as transcription activation by Cat8, is affected by carbon source (Rahner et al, 1996 ;RandezGil et al, 1997). A functional Cat1\Snf1\Ccr1 protein kinase together with its auxiliary factors Cat3\Snf4 (Celenza & Carlson, 1986 ;Schu$ ller & Entian, 1987, 1988Celenza et al, 1989) and Sip1jSip2jGal83 (Yang et al, 1994 ;Schmidt & McCartney, 2000) is absolutely required for Cat8 function.…”