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Saccharomyces cerevisiae Rim101 is a member of the fungal PacC family of transcription factors involved
in the response to alkaline pH stress. Further studies have also implicated Rim101 in the responses to
other stresses, and have shown its genetic interaction with the iron deprivation-responsive factor Aft1.
The present study shows that the absence of Rim101 leads to hypersensitivity to oxidants such as t-butyl
hydroperoxide and diamide, and also to the prooxidant agent selenite. The protective role of Rim101
against selenite requires the sensing complex component Rim8, the ESCRT-I/II/III complexes and the
Rim13 protease involved in proteolytic activation of Rim101. The Nrg1 transcriptional repressor is a
downstream effector of Rim101 in this response to selenite, as occurs in the responses to alkaline pH,
Na+ and Li+ stresses. Deletion of RIM101 causes downregulation of the vacuolar ATPase genes VMA2
and VMA4, which becomes accentuated compared to wild type cells upon selenite stress, and activation
of the Rim101 protein prevents inhibition of vacuolar acidification caused by selenite. These observations
therefore support a role of Rim101 in modulation of vacuolar acidity necessary for selenite detoxification.
In addition, a parallel Rim101-independent pathway requiring the complete ESCRT machinery (including
the ESCRT-0 complex) also participates in protection against selenite.
This work was supported by Grants BFU2010-17656 (from Ministerio de Economía y Competitividad, Spain) and 2009/SGR/196 (from Generalitat de Catalunya). |
