SUT1 is a putative Zn[II]2Cys6‐transcription factor whose upregulation enhances both sterol uptake and synthesis in aerobically growing Saccharomyces cerevisiae cells

Abstract

Budding yeast Saccharomyces cerevisiae is a facultative anaerobe whose growth upon oxygen starvation depends on its capacity to import exogenously supplied sterols, whereas the cells are not permeable to these molecules when grown aerobically. Few genes have been identified as being involved in sterol uptake. A higher SUT1 gene dosage leads to a modest, but significant, increase in sterol uptake under aerobic conditions. Based on sequence and physiological data, SUT1 is a hypoxic gene negatively regulated when the cells are grown in the presence of oxygen. We replaced the SUT1 promoter with the constitutive PMA1 gene promoter in order to enhance its transcription. We observed that sterol uptake was then comparable with that obtained with a sterol importing hem1 mutant, although the heme status of the strain was not modified in a process which still occurs when the cells are not growing. Unexpectedly, SUT1 constitutive expression led to a parallel significant increase in endogenous sterol biosynthesis. Moreover, here we present new data showing that the structurally related YPR009 gene (SUT2) is a functional homologue of SUT1, and that both gene products may represent two novel yeast regulatory proteins involved in sterol uptake.

The Cdc42 Effectors Ste20, Cla4, and Skm1 Down-Regulate the Expression of Genes Involved in Sterol Uptake by a Mitogen-activated Protein Kinase-independent Pathway

“…By using pull-down assays, we demonstrate that not only Ste20 but also Cla4 and Skm1 bind to Sut1. Sut1 localizes exclusively to the nucleus, even after strong overexpression (data not shown) (Ness et al, 2001). Thus far, Ste20 and Cla4 have been shown to localize mainly to the plasma membrane at sites of polarized growth and to the cytoplasm, whereas the localization of Skm1 has not been reported previously (Peter et al, 1996;Leberer et al, 1997;Holly and Blumer 1999).…”

“…To gain insight into molecular mechanisms of Ste20 action, we screened for interactors of Ste20 using the split-ubiquitin technique (Tiedje et al, 2007). Here, we show that Sut1, a transcriptional regulator that controls sterol uptake (Bourot and Karst, 1995;Ness et al, 2001), forms a complex with Ste20. By using pull-down assays, we demonstrate that not only Ste20 but also Cla4 and Skm1 bind to Sut1.…”

“…Sut1 localizes to the nucleus (Ness et al, 2001), whereas Ste20 can be found in the cytosol and at the plasma membrane at sites of polarized growth (Peter et al, 1996;Leberer et al, 1997) (Figure 3B). Therefore, it is not clear where the interaction between Sut1 and Ste20 takes place.…”

“…By using this technique, we identified Sut1 as a putative Ste20-interacting protein (Figure 2B). SUT1 encodes a transcriptional regulator involved in sterol uptake under anaerobic conditions (Bourot and Karst, 1995;Ness et al, 2001). To confirm the interaction between Ste20 and Sut1 by an independent approach, recombinant GST and GST-Sut1 purified from E. coli were bound to glutathione-Sepharose beads, which were then incubated with a yeast extract of STE20-3HA cells.…”

Regulation of hypoxia adaptation: an overlooked virulence attribute of pathogenic fungi?

“…Studies of several other hypoxic/anaerobic genes including SUT1, encoding a putative Zn[II]2Cys6-transcription factor that facilitates the uptake and synthesis of sterols under hypoxic conditions (57), GPD2, encoding an isoenzyme of NAD-dependent glycerol 3-phosphate dehydrogenase (58), and members of the seripauperine (PAU) family, like TIR1 (59) have demonstrated Rox1p-independent hypoxic/anaerobic induction, but the mechanisms by which this occurs are not yet understood.…”