The Transcriptional Activator Imp2p Maintains Ion Homeostasis in Saccharomyces cerevisiae

Corresponding author: Dindial Ramotar, Maisonneuve-Rosemont Hospital Research Center, 5415 de l’Assomption Boul., Montreal, Quebec, H1T 2M4, Canada, dramotar{at}hmr.qc.ca (E-mail).

Communicating editor: P. G. YOUNG

Yeast cells deficient in the transcriptional activator Imp2p are viable, but display marked hypersensitivity to a variety of oxidative agents. We now report that imp2 null mutants are also extremely sensitive to elevated levels of the monovalent ions, Na⁺ and Li⁺, as well as to the divalent ions Ca²⁺, Mn²⁺, Zn²⁺, and Cu²⁺, but not to Cd²⁺, Mg²⁺, Co²⁺, Ni²⁺, and Fe²⁺, as compared to the parent strain. We next searched for multicopy suppressor genes that would allow the imp2 mutant to grow under high salt conditions. Two genes that independently restored normal salt-resistance to the imp2 mutant, ENA1 and HAL3, were isolated. ENA1 encodes a P-type ion pump involved in monovalent ion efflux from the cell, while HAL3 encodes a protein required for activating the expression of Ena1p. Neither ENA1 nor HAL3 gene expression was positively regulated by Imp2p. Moreover, the imp2 ena1 double mutant was exquisitely sensitive to Na⁺/Li⁺ cations, as compared to either single mutant, implying that Imp2p mediates Na⁺/Li⁺ cation homeostasis independently of Ena1p.

This article has been cited by other articles:

				C. Papdi, E. Abraham, M. P. Joseph, C. Popescu, C. Koncz, and L. Szabados Functional Identification of Arabidopsis Stress Regulatory Genes Using the Controlled cDNA Overexpression System Plant Physiology, June 1, 2008; 147(2): 528 - 542. [Abstract] [Full Text] [PDF]

				R. Vongsamphanh, P.-K. Fortier, and D. Ramotar Pir1p Mediates Translocation of the Yeast Apn1p Endonuclease into the Mitochondria To Maintain Genomic Stability Mol. Cell. Biol., March 1, 2001; 21(5): 1647 - 1655. [Abstract] [Full Text]

				C. A. Masuda, J. Ramirez, A. Pena, and M. Montero-Lomeli Regulation of Monovalent Ion Homeostasis and pH by the Ser-Thr Protein Phosphatase SIT4 in Saccharomyces cerevisiae J. Biol. Chem., September 29, 2000; 275(40): 30957 - 30961. [Abstract] [Full Text] [PDF]