Whi2 or Whiskey 2 is a 55 kDa

globular A globular cluster is a spheroidal conglomeration of stars that is bound together by gravity, with a higher concentration of stars towards its center. It can contain anywhere from tens of thousands to many millions of member stars, all orbiting ...

scaffold protein In biology, scaffold proteins are crucial regulators of many key signalling pathways. Although scaffolds are not strictly defined in function, they are known to interact and/or bind with multiple members of a signalling pathway, tethering them in ...

located to cell periphery in

Saccharomyces cerevisiae ''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungal microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have be ...

, which plays an essential role in regulating stress response pathways, apparently by passing input signals about nutrient availability on to stress responsive elements and autophagy/mitophagy mechanisms. It is encoded by a 1.46 kbp gene located on chromosome 15. Whi2p shares a conserved BTB structure domain to the family of human potassium channel tetramerization domain proteins (KCTDs). KCTD family members have been associated with several type of cancers and epilepsy disorders.

Functional mechanism

Upon complexing with plasma membrane associated phosphatas
Psr1
an
Psr2
Whi2 induces general stress response by dephosphorylating general stress response transcription factor Msn2. Whi2 is essential for Msn2 activity, moreover activation by Whi2 is dominant and independent of the

PKA In chemistry, an acid dissociation constant (also known as acidity constant, or acid-ionization constant; denoted ) is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction :H ...

and TOR activation pathways. Additionally, experiments suggests Whi2 plays a role in

Ras2 Ras2 is a ''Saccharomyces cerevisiae'' guanine nucleotide-binding protein (encoded by the RAS2 gene) which becomes activated by binding Guanosine triphosphate, GTP when glucose is present in the environment. It affects growth regulation and starvati ...

deactivation or degradation during nutrient depletion. Whi2-Psr1/Psr2 complex is also required for inhibition of TORC1 activity under conditions of nutrient deprivation. Furthermore, a striking characteristic of Whi2 is the repeated observation of spontaneous mutations in the ''WHI2'' gene in the yeast library of knock-out strains and in genome evolutionary studies. Recently a novel function of Whi2-Psr1/Psr2 complex identified in balancing cell population and regulating expansion of cells with fitness advantage in dense yeast populations.

References

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