Characterization of TUP1, a mediator of glucose repression in Saccharomyces cerevisiae.

Abstract

The TUPI and CYC8 (=SSN6) genes of Saccharomyces cerevisiae play a major role in glucose repression. Mutations in either TUPI or CYC8 eliminate or reduce glucose repression of many repressible genes and induce other phenotypes, including flocculence, failure to sporulate, and sterility of MATa cells. The TUP) gene was isolated in a screen for genes that regulate mating type (V. L. MacKay, Methods Enzymol. 101:325-343, 1983). We found that a 3.5-kb restriction fragment was sufficient for complete complementation of tupl-100. (21,34,44,49).tupi and cyc8 mutants share many phenotypes, including calcium-dependent flocculation (34,36,50), mating-type defects in MATa cells (5,20,34,54), nonsporulation of * Corresponding author.homozygous diploids (34, 36), and derepression of many enzymes under glucose repression. The diversity of phenotypes may arise from the involvement of TUPI and CYC8 in regulatory pathways distinct from glucose repression or may reflect the interaction of glucose repression with these pathways.SNFJ (CCRI, CATJ) encodes a protein kinase that is necessary for the derepression of glucose-repressible genes (6, 9). Mutant snfl strains cannot ferment sucrose or utilize other nonfermentable carbon sources. Some of these effects are suppressed by cyc8 mutations. Double snfl cyc8 mutants are constitutive for invertase synthesis (6). It has been postulated that CYC8 is a negative regulator of glucose repression and that SNFJ may act through CYC8 (6).Mutations in TUPI and CYC8 produce the same array of phenotypes, suggesting that the two genes function at similar points in regulation. However, their specific roles and the mechanism of glucose repression are still unknown, although the latter seems to involve multiple steps or pathways (11,27). Possible roles for TUPI and CYC8 as negative regulators could be repression of transcription or interference of activation of transcription. Recently CYC8 (SSN6) was cloned, characterized, and sequenced (37, 51). However, no functional role has yet been identified for the CYC8 gene product. To further understand the roles of TUP1 and CYC8 in catabolite repression, TUPI has been characterized and sequenced. This work is described here. MATERIALS AND METHODSStrains and media. The Saccharomyces cerevisiae strains used (Table 1)

A Complex Composed of Tup1 and Ssn6 Represses Transcription in Vitro

“…: 415-476-8783; Fax: 415-476-0939. 1 The abbreviations used are: GST, glutathione S-transferase; DTT, dithiothreitol; PAGE, polyacrylamide gel electrophoresis; TBST, Trisbuffered saline plus 5% milk and 0.2% Tween; TPR, tetratricopeptide repeat.…”

“…However, an increasing number of WD repeat proteins have been identified that are nuclear localized and function in the repression of transcription. These include Tup1, Hir1, and Met30 in S. cerevisiae; SCON2 in Neurospora crassa; extra sex combs and groucho in Drosophila; COP1 in Arabidopsis thaliana; and HIRA and the family of TLE proteins in humans (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). These WD repeat repressor proteins turn off a wide variety of genes, including those involved in segmentation, sex determination, and neurogenesis (controlled by groucho) and those involved in photomorphogenesis (controlled by COP1) (7,11).…”

Cloning of two related genes encoding the 56‐kDa and 123‐kDa subunits of trehalose synthase from the yeast Saccharomyces cerevisiae

“…Glutamine-rich sequences are found in many regulatory proteins and it has been speculated they may mediate interactions between domains (Williams and Trumbly, 1990). The second of these polyglutamine sequences forms part of a repeat of the sequence RIASPIQ.…”

Glucose repression in the yeast Saccharomyces cerevisiae

“…1987;Trumbly. 1988;Williams and Trumbly, 1990), The CYC8 protein contains 10 copies of the 34-amino-acid tetratricopeptide (TPR) repeat near the W-terminus (Sikorski etai, 1990;Hirano et ai. 1990), and these repeats are required for CYC8 function (Schultz etat., 1990).…”