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Gene Review

SKO1  -  Sko1p

Saccharomyces cerevisiae S288c

Synonyms: ACR1, CRE-binding bZIP protein SKO1, N1702, YNL167C
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Disease relevance of SKO1


High impact information on SKO1

  • During hyperosmotic stress, Hog1 MAP kinase associates with target promoters, phosphorylates Sko1, and converts Sko1 into a transcriptional activator [3].
  • Here we demonstrate that the ion homeostasis determinant, HAL1, is regulated by two antagonistically operating bZIP transcription factors, the Sko1p repressor and the Gcn4p activator [4].
  • The Sko1p repressor and Gcn4p activator antagonistically modulate stress-regulated transcription in Saccharomyces cerevisiae [4].
  • In addition, Acr1 does not affect a number of phenotypes that arise from loss of Aca2 [5].
  • A glutathione S-transferase-Sko1 fusion protein binds specifically to the URSCRE-ENA1 element [6].

Biological context of SKO1

  • All five Sko1p target genes are induced by oxidative stress, and induction involves Yap1p [7].
  • The ATF/CREB consensus sequence is not statistically overrepresented in confirmed Sko1 target promoters, although some sites are evolutionarily conserved among related yeast species, suggesting that they are functionally important in vivo [8].
  • Taken together our results suggest that Sko1 operates a transcriptional network upon osmotic stress, which involves other specific transcription factors and a phosphatase that regulates the key component of the signal transduction pathway [8].
  • The central part (315) of Sko1p, containing the PKA phosphorylation sites and the basic domain-leucine zipper domain, is essential for its nuclear localization [9].
  • We analyzed the function of the SACE of the left arm of chromosome VIII in vivo and found its ATF/CREB site to act as UAS/URS of the COS8 promoter, effected by the yeast bZip proteins Sko1p, Aca1p, and Aca2p [10].

Anatomical context of SKO1

  • Sko1p is localized in the nucleus of unstressed cells, and it redistributes to the cytosol upon severe salt stress (1 m NaCl) [9].
  • Interestingly, Sko1p, a downstream regulator of the high osmolarity pathway is known to bind to the AFT/CRE binding site, suggesting a possible role for the Hog1 pathway in the response to cell wall stress [11].

Associations of SKO1 with chemical compounds

  • Within the bZIP domain, ACR1 most strongly resembles the mammalian cyclic AMP-responsive transcriptional regulators CREB and CREM; it is less similar to GCN4 and YAP1, two previously described yeast bZIP transcriptional activators that recognize the related AP-1 sequence (consensus TGACTCA) [12].
  • The cluster of three genes, ACR1, ACR2, and ACR3, previously was shown to confer arsenical resistance in Saccharomyces cerevisiae [13].
  • In contrast, acr1, acr3, and acr4 mutants were resistant to papulacandin B (an antibiotic containing a disaccharide linked to two fatty acid chains that also inhibits beta-glucan synthesis), but acr2 mutants were susceptible to this antibiotic [14].

Physical interactions of SKO1

  • We found that SKO1 also binds to a CRE-like site in SUC2, a yeast gene encoding invertase which is under positive control by cAMP [15].

Enzymatic interactions of SKO1


Other interactions of SKO1

  • Repressors and upstream repressing sequences of the stress-regulated ENA1 gene in Saccharomyces cerevisiae: bZIP protein Sko1p confers HOG-dependent osmotic regulation [6].
  • Studies with the yeast transcription factors GCN4, SKO1 and YAP1, which bind CRE-like sequences, showed no influence on expression of the 35S promoter indicating that a yet unknown factor is involved in activation [17].
  • Acr1 does not fully account for osmotic regulation through ATF/CREB sites, and a novel Hog1-dependent activator(s) that is not a bZIP protein is required for ATF/CREB site activation in response to high salt [5].
  • Sko1p repressor activity is associated to its binding to the Ssn6p x Tup1p complex [9].
  • Salt-induced export of Sko1p from the nucleus is independent of Hog1p and of the Bcy1p regulatory subunit of PKA [9].
  • The results thus provide evidence that Plc1p and inositol polyphosphates affect derepression of Sko1p-Ssn6p-Tup1p-controlled genes by a mechanism that involves recruitment of the SAGA complex and TATA-binding protein [18].

Analytical, diagnostic and therapeutic context of SKO1

  • By combining chromatin immunoprecipitation and microarrays containing essentially all intergenic regions, we estimate that yeast cells contain approximately 40 Sko1 target promoters in vivo; 20 Sko1 target promoters were validated by direct analysis of individual loci [8].


  1. Molecular and genetic analysis of the toxic effect of RAP1 overexpression in yeast. Freeman, K., Gwadz, M., Shore, D. Genetics (1995) [Pubmed]
  2. Isolation of three contiguous genes, ACR1, ACR2 and ACR3, involved in resistance to arsenic compounds in the yeast Saccharomyces cerevisiae. Bobrowicz, P., Wysocki, R., Owsianik, G., Goffeau, A., Ułaszewski, S. Yeast (1997) [Pubmed]
  3. Hog1 kinase converts the Sko1-Cyc8-Tup1 repressor complex into an activator that recruits SAGA and SWI/SNF in response to osmotic stress. Proft, M., Struhl, K. Mol. Cell (2002) [Pubmed]
  4. The Sko1p repressor and Gcn4p activator antagonistically modulate stress-regulated transcription in Saccharomyces cerevisiae. Pascual-Ahuir, A., Serrano, R., Proft, M. Mol. Cell. Biol. (2001) [Pubmed]
  5. Aca1 and Aca2, ATF/CREB activators in Saccharomyces cerevisiae, are important for carbon source utilization but not the response to stress. Garcia-Gimeno, M.A., Struhl, K. Mol. Cell. Biol. (2000) [Pubmed]
  6. Repressors and upstream repressing sequences of the stress-regulated ENA1 gene in Saccharomyces cerevisiae: bZIP protein Sko1p confers HOG-dependent osmotic regulation. Proft, M., Serrano, R. Mol. Cell. Biol. (1999) [Pubmed]
  7. The Saccharomyces cerevisiae Sko1p transcription factor mediates HOG pathway-dependent osmotic regulation of a set of genes encoding enzymes implicated in protection from oxidative damage. Rep, M., Proft, M., Remize, F., Tamás, M., Serrano, R., Thevelein, J.M., Hohmann, S. Mol. Microbiol. (2001) [Pubmed]
  8. Genomewide identification of Sko1 target promoters reveals a regulatory network that operates in response to osmotic stress in Saccharomyces cerevisiae. Proft, M., Gibbons, F.D., Copeland, M., Roth, F.P., Struhl, K. Eukaryotic Cell (2005) [Pubmed]
  9. Multiple levels of control regulate the yeast cAMP-response element-binding protein repressor Sko1p in response to stress. Pascual-Ahuir, A., Posas, F., Serrano, R., Proft, M. J. Biol. Chem. (2001) [Pubmed]
  10. ATF/CREB sites present in sub-telomeric regions of Saccharomyces cerevisiae chromosomes are part of promoters and act as UAS/URS of highly conserved COS genes. Spode, I., Maiwald, D., Hollenberg, C.P., Suckow, M. J. Mol. Biol. (2002) [Pubmed]
  11. Characterization of the transcriptional response to cell wall stress in Saccharomyces cerevisiae. Boorsma, A., de Nobel, H., ter Riet, B., Bargmann, B., Brul, S., Hellingwerf, K.J., Klis, F.M. Yeast (2004) [Pubmed]
  12. ACR1, a yeast ATF/CREB repressor. Vincent, A.C., Struhl, K. Mol. Cell. Biol. (1992) [Pubmed]
  13. The Saccharomyces cerevisiae ACR3 gene encodes a putative membrane protein involved in arsenite transport. Wysocki, R., Bobrowicz, P., Ułaszewski, S. J. Biol. Chem. (1997) [Pubmed]
  14. Isolation and characterization of Saccharomyces cerevisiae mutants resistant to aculeacin A. Font de Mora, J., Gil, R., Sentandreu, R., Herrero, E. Antimicrob. Agents Chemother. (1991) [Pubmed]
  15. Yeast SKO1 gene encodes a bZIP protein that binds to the CRE motif and acts as a repressor of transcription. Nehlin, J.O., Carlberg, M., Ronne, H. Nucleic Acids Res. (1992) [Pubmed]
  16. Regulation of the Sko1 transcriptional repressor by the Hog1 MAP kinase in response to osmotic stress. Proft, M., Pascual-Ahuir, A., de Nadal, E., Ariño, J., Serrano, R., Posas, F. EMBO J. (2001) [Pubmed]
  17. The plant transcription factor TGA1 stimulates expression of the CaMV 35S promoter in Saccharomyces cerevisiae. Rüth, J., Schweyen, R.J., Hirt, H. Plant Mol. Biol. (1994) [Pubmed]
  18. Plc1p is required for SAGA recruitment and derepression of Sko1p-regulated genes. Guha, N., Desai, P., Vancura, A. Mol. Biol. Cell (2007) [Pubmed]
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