Nutrients, via the Tor proteins, stimulate the association of Tap42 with type 2A phosphatases.

Abstract

We identified an essential Saccharomyces cerevisiae protein, Tap42, that associates with Sit4, a type 2A-related protein phosphatase, and with the type 2A phosphatase catalytic subunits. The association of Tap42 with the phosphatases does not require the previously identified phosphatase subunits. Genetic analysis suggests that Tap42 functions positively with both phosphatases. Mutations in TAP42 can confer almost complete rapamycin resistance. In addition, Tap42/Sit4 and Tap42/PP2A complex formation is regulated by nutrient growth signals and the rapamycin-sensitive Tor signaling pathway. These findings, combined with the defect in translation of the tap42-11 mutant at the nonpermissive temperature, suggest that Tap42, Sit4, and PP2A are components of the Tot signaling pathway.

Functional characterization of Fusarium verticillioides CPP1, a gene encoding a putative protein phosphatase 2A catalytic subunit

“…cerevisiae clearly indicates that Cpp1 has the highest homology with Sit4 (76 % identity, 84 % similarity). Sit4 is a component of the conserved TOR (the target of rapamycin) signalling pathway (Di Como & Arndt, 1996) that interacts with Tap42, the phosphatase regulatory subunit of the TOR pathway, in response to nutrient stress (Cutler et al, 2001). Considering the similarity between Sit4 and Cpp1, we hypothesized that hyphal swelling in PP179 may be caused by the defect in nutritional stress response, and perhaps this process is mediated by F. verticillioides Tap42 homologue (FVEG_06413.3) (Fig.…”

Target of rapamycin (TOR): an integrator of nutrient and growth factor signals and coordinator of cell growth and cell cycle progression

“…In a nutrient-dependent manner, yeast TOR proteins stimulate the association of the phosphatases Sit4 (PP6-like) and Pph21/22 (PP2A-like) with the phosphatase-interacting protein, Tap42, an interaction that results in the inhibition of phosphatase function by competing out other regulatory subunits (Di Como and Arndt, 1996;Jiang and Broach, 1999). Consistent with a role for TOR in regulating the Tap42/phosphatase interaction, nutrient deprivation or rapamycin induces dissociation of the Tap42/phosphatase complex, and mutations in Tap42 confer rapamycin resistance (Di Como and Arndt, 1996;Jiang and Broach, 1999). Recently, the TAP42-interacting protein, TIP41, was identified as a novel regulator of Tap42 and Sit4 (Jacinto et al, 2001).…”

Differential regulation of cell wall biogenesis during growth and development in yeast

“…Rho1p is, through Rom2p, activated by the phosphatidylinositol kinase homologue Tor2p (Schmidt et al, 1997). Tor2p is involved in the regulation of translation initiation and through that in cell cycle progression in G1, probably in response to nutritional conditions (Barbet et al, 1996 ;Di Como & Arndt, 1996) (Fig. 3a).…”