Involvement of Spt7p in vacuolar polyphosphate level of Saccharomyces cerevisiae.

Saccharomyces cerevisiae became less sensitive to nickel by a defect of the SPT7 gene encoding a transcription factor. Initial rate of nickel uptake by whole cells of a SPT7-negative mutant FY963 was nearly equal to that of the parent strain FY61, and FY963 accumulated nickel about 1.7-fold of the value of FY61 when cultured in medium containing 0.1 mM NiCl2; most of which was sequestered into vacuoles. The pH gradient-driven nickel uptake by vacuolar membrane vesicles was not altered in FY963, but the amount of polyphosphate in vacuoles was highly elevated. Involvement of Spt7p in nickel detoxification through regulation of vacuolar polyphosphate level in S. cerevisiae was discussed.