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Gene Review

PBS2  -  Pbs2p

Saccharomyces cerevisiae S288c

Synonyms: HOG4, J0699, MAP kinase kinase PBS2, Polymyxin B resistance protein 2, SFS4, ...
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Disease relevance of PBS2

  • Serotype A hog1delta and pbs2delta mutants are attenuated in virulence, further underscoring the role of the Pbs2-Hog1 MAPK cascade in the pathogenesis of cryptococcosis [1].

High impact information on PBS2

  • Osmotic activation of the HOG MAPK pathway via Ste11p MAPKKK: scaffold role of Pbs2p MAPKK [2].
  • Alternatively, Pbs2p was activated by a mechanism that involves the binding of its amino terminal proline-rich motif to the Src homology 3 (SH3) domain of a putative transmembrane osmosensor Sho1p [3].
  • A rapid, PBS2-dependent tyrosine phosphorylation of HOG1 protein occurred in response to increases in extracellular osmolarity [4].
  • The pbs2 mutation enhanced the rga1 mutant phenotype, but by itself did not activate the pheromone pathway [5].
  • To investigate this issue, we engineered a series of mutants that incrementally reduced the affinity of the yeast Sho1p SH3 domain for its in vivo target, the MAP kinase kinase Pbs2p [6].

Biological context of PBS2

  • EXG1 and PBS2 were isolated as genes that, when expressed from multicopy plasmids, led to a dominant killer toxin-resistant phenotype [7].
  • One of these plasmids carried PBS2, a previously identified, non-essential gene which produces a variety of phenotypes and encodes a mitogen-activated protein kinase kinase analogue (Boguslawski and Polazzi, 1987) [8].
  • We show that Hog1 is robustly phosphorylated in a Pbs2-dependent way during oxidative stress, and that Rck2 also is phosphorylated under these circumstances [9].
  • The HOG signal pathway of the yeast Saccharomyces cerevisiae is defined by the PBS2 and HOG1 genes encoding members of the MAP kinase kinase and of the MAP kinase family, respectively [10].
  • Mutations in this pathway (deletions of PBS2 or HOG1, or point mutations in HOG1) almost completely abolish the induction of transcription by osmotic stress that is mediated by stress response elements (STREs) [10].

Anatomical context of PBS2

  • Cells carrying PBS2 at multiple copy show a small decrease in cell wall beta(1-6) glucans [8].
  • One branch is dependent on the Sho1 transmembrane protein, whose primary role was found to be the binding and translocation of the Pbs2 MAPKK to the plasma membrane, and specifically to sites of polarized growth [11].

Associations of PBS2 with chemical compounds

  • Measurements of beta(1-3) glucan synthase activity in multi-copy PBS2 cells showed an approximate 30-45% increase in enzyme specific activity while a pbs2 delta disruption strain showed a decrease in glucan synthase activity of approximately 45% relative to control [8].
  • Regulation of cell wall beta-glucan assembly: PTC1 negatively affects PBS2 action in a pathway that includes modulation of EXG1 transcription [7].
  • ALD2 exhibits maximum induction with 0.3 M NaCl, negative regulation by protein kinase A and dependence on PBS2 and HOG1 protein kinases for osmotic induction [12].
  • We deleted the PBS2 gene encoding the MAP kinase activator of the osmosignaling HOG pathway in Saccharomyces cerevisiae and examined the effects on the kinetics of the osmoregulatory glycerol response and protein induction during adaptation to 0.7 M NaCl [13].
  • The gene, PBS2, located on chromosome X, is not allelic to the previously described PBS1 gene (where PBS signifies polymyxin B sensitivity) [14].

Physical interactions of PBS2

  • In addition, the Pbs2 scaffold bound the Nbp2 SH3 via a Pro-rich motif distinct from that which binds the SH3 domain of the positive regulator Sho1 [15].
  • Pbs2p requires its Pro-rich motif for binding to the Src-homology3 (SH3) domain of Sho1p, but PbsB lacks a typical Pro-rich motif [16].

Regulatory relationships of PBS2

  • One of these proteins, Sho1, utilizes the MAP kinase kinase kinase Ste11 to activate Pbs2 [17].
  • Evidence that C-terminal non-kinase domain of Pbs2p has a role in high osmolarity-induced nuclear localization of Hog1p [18].
  • We cloned and characterized Neurospora NcSSK22 and NcPBS2 genes, similar to yeast SSK22 mitogen-activated protein (MAP) kinase kinase kinase and the PBS2 MAP kinase kinase genes, respectively [19].

Other interactions of PBS2

  • We found that mutations in the HOG1 gene, encoding the p38-type MAPK of the HOG pathway, and in the PBS2 gene, encoding the activating kinase for Hog1p, allowed osmolarity-induced activation of the pheromone response pathway [20].
  • These results suggest that Ptc1p/Cwh47p and Pbs2p play opposing regulatory roles in cell wall glucan assembly, and that this is effected in part by modulating Exg1p activity [7].
  • Multiple copies of PBS2, MHP1 or LRE1 produce glucanase resistance and other cell wall effects in Saccharomyces cerevisiae [8].
  • Deletion of either PBS2 or HOG1 alleviates the slow growth phenotype of ptc1delta skn7delta cells, suggesting that Skn7p may participate, in concert with known regulatory components, in modulating HOG pathway activity [21].
  • In a fraction of untreated pbs2 cells, Yap2 is nuclear [9].


  1. Specialization of the HOG pathway and its impact on differentiation and virulence of Cryptococcus neoformans. Bahn, Y.S., Kojima, K., Cox, G.M., Heitman, J. Mol. Biol. Cell (2005) [Pubmed]
  2. Osmotic activation of the HOG MAPK pathway via Ste11p MAPKKK: scaffold role of Pbs2p MAPKK. Posas, F., Saito, H. Science (1997) [Pubmed]
  3. Activation of yeast PBS2 MAPKK by MAPKKKs or by binding of an SH3-containing osmosensor. Maeda, T., Takekawa, M., Saito, H. Science (1995) [Pubmed]
  4. An osmosensing signal transduction pathway in yeast. Brewster, J.L., de Valoir, T., Dwyer, N.D., Winter, E., Gustin, M.C. Science (1993) [Pubmed]
  5. Mutation of RGA1, which encodes a putative GTPase-activating protein for the polarity-establishment protein Cdc42p, activates the pheromone-response pathway in the yeast Saccharomyces cerevisiae. Stevenson, B.J., Ferguson, B., De Virgilio, C., Bi, E., Pringle, J.R., Ammerer, G., Sprague, G.F. Genes Dev. (1995) [Pubmed]
  6. Protein-protein interaction affinity plays a crucial role in controlling the Sho1p-mediated signal transduction pathway in yeast. Marles, J.A., Dahesh, S., Haynes, J., Andrews, B.J., Davidson, A.R. Mol. Cell (2004) [Pubmed]
  7. Regulation of cell wall beta-glucan assembly: PTC1 negatively affects PBS2 action in a pathway that includes modulation of EXG1 transcription. Jiang, B., Ram, A.F., Sheraton, J., Klis, F.M., Bussey, H. Mol. Gen. Genet. (1995) [Pubmed]
  8. Multiple copies of PBS2, MHP1 or LRE1 produce glucanase resistance and other cell wall effects in Saccharomyces cerevisiae. Lai, M.H., Silverman, S.J., Gaughran, J.P., Kirsch, D.R. Yeast (1997) [Pubmed]
  9. Rck1 and Rck2 MAPKAP kinases and the HOG pathway are required for oxidative stress resistance. Bilsland, E., Molin, C., Swaminathan, S., Ramne, A., Sunnerhagen, P. Mol. Microbiol. (2004) [Pubmed]
  10. The HOG pathway controls osmotic regulation of transcription via the stress response element (STRE) of the Saccharomyces cerevisiae CTT1 gene. Schüller, C., Brewster, J.L., Alexander, M.R., Gustin, M.C., Ruis, H. EMBO J. (1994) [Pubmed]
  11. Yeast Cdc42 GTPase and Ste20 PAK-like kinase regulate Sho1-dependent activation of the Hog1 MAPK pathway. Raitt, D.C., Posas, F., Saito, H. EMBO J. (2000) [Pubmed]
  12. A genomic locus in Saccharomyces cerevisiae with four genes up-regulated by osmotic stress. Miralles, V.J., Serrano, R. Mol. Microbiol. (1995) [Pubmed]
  13. Osmoregulation and protein expression in a pbs2delta mutant of Saccharomyces cerevisiae during adaptation to hypersaline stress. Akhtar, N., Blomberg, A., Adler, L. FEBS Lett. (1997) [Pubmed]
  14. Complete nucleotide sequence of a gene conferring polymyxin B resistance on yeast: similarity of the predicted polypeptide to protein kinases. Boguslawski, G., Polazzi, J.O. Proc. Natl. Acad. Sci. U.S.A. (1987) [Pubmed]
  15. Nbp2 targets the Ptc1-type 2C Ser/Thr phosphatase to the HOG MAPK pathway. Mapes, J., Ota, I.M. EMBO J. (2004) [Pubmed]
  16. Aspergillus nidulans HOG pathway is activated only by two-component signalling pathway in response to osmotic stress. Furukawa, K., Hoshi, Y., Maeda, T., Nakajima, T., Abe, K. Mol. Microbiol. (2005) [Pubmed]
  17. A third osmosensing branch in Saccharomyces cerevisiae requires the Msb2 protein and functions in parallel with the Sho1 branch. O'Rourke, S.M., Herskowitz, I. Mol. Cell. Biol. (2002) [Pubmed]
  18. Evidence that C-terminal non-kinase domain of Pbs2p has a role in high osmolarity-induced nuclear localization of Hog1p. Sharma, P., Mondal, A.K. Biochem. Biophys. Res. Commun. (2005) [Pubmed]
  19. Putative homologs of SSK22 MAPKK kinase and PBS2 MAPK kinase of Saccharomyces cerevisiae encoded by os-4 and os-5 genes for osmotic sensitivity and fungicide resistance in Neurospora crassa. Fujimura, M., Ochiai, N., Oshima, M., Motoyama, T., Ichiishi, A., Usami, R., Horikoshi, K., Yamaguchi, I. Biosci. Biotechnol. Biochem. (2003) [Pubmed]
  20. The Hog1 MAPK prevents cross talk between the HOG and pheromone response MAPK pathways in Saccharomyces cerevisiae. O'Rourke, S.M., Herskowitz, I. Genes Dev. (1998) [Pubmed]
  21. Yeast Skn7p activity is modulated by the Sln1p-Ypd1p osmosensor and contributes to regulation of the HOG pathway. Ketela, T., Brown, J.L., Stewart, R.C., Bussey, H. Mol. Gen. Genet. (1998) [Pubmed]
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