Abstract
The SUN family consists of 4 genes (SIM1, UTH1, SUN4 and NCA3) coding for proteins homologous in their Cterminal amino acid domain. SUN family proteins are involved in various cellular functions and processes (cell wall/mitochondrial biogenesis, mitophagy, oxidative stress resistance and others).
Uth1p and Sun4p have dual cell wall/mitochondrial localization. Here, we show that Uth1p, Sim1p and Sun4p are secreted by cells grown in liquid cultures and these proteins are present in the extracellular space of developing colonies.
The amount of SUN proteins depends on growth phase and their production is regulated differently according to the level of oxygen. SUN-protein-deficient strains have different sensitivities to the cell wall damaging agents Congo red and CFW, the fungicide boric acid and zymolyase treatment.
Sensitivities of SUN-protein-deficient strains to toxic compounds differ in cells grown on different carbon sources. In summary, our findings support the hypothesis that Sun family proteins are involved in the remodeling of the yeast cell wall during yeast culture development and under various environmental conditions.
The finding that cell sensitivity to boric acid depends on Uth1p makes this protein a target for studies of boric acid's action