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Molecular and Cellular Biology, January 2001, p. 175-184, Vol. 21, No. 1
Department of Molecular Genetics, The
Weizmann Institute of Science, Rehovot 76100, Israel
Received 15 September 2000/Accepted 12 October 2000
Although most cells are capable of transporting polyamines, the
mechanism that regulates polyamine transport in eukaryotes is still
largely unknown. Using a genetic screen for clones capable of restoring
spermine sensitivity to spermine-tolerant mutants of
Saccharomyces cerevisiae, we have demonstrated that Sky1p, a recently identified SR protein kinase, is a key regulator of polyamine transport. Yeast cells deleted for SKY1 developed
tolerance to toxic levels of spermine, while overexpression of Sky1p in wild-type cells increased their sensitivity to spermine. Expression of
the wild-type Sky1p but not of a catalytically inactive mutant restored
sensitivity to spermine. SKY1 disruption results in
dramatically reduced uptake of spermine, spermidine, and putrescine. In
addition to spermine tolerance, sky1
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.1.175-184.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Screening for Modulators of Spermine Tolerance
Identifies Sky1, the SR Protein Kinase of Saccharomyces
cerevisiae, as a Regulator of Polyamine Transport and Ion
Homeostasis
cells exhibit
increased tolerance to lithium and sodium ions but somewhat increased
sensitivity to osmotic shock. The observed halotolerance suggests
potential regulatory interaction between the transport of polyamines
and inorganic ions, as suggested in the case of the Ptk2p, a recently described regulator of polyamine transport. We demonstrate that these
two kinases act in two different signaling pathways. While deletion or
overexpression of SKY1 did not significantly affect Pma1p
activity, the ability of overexpressed Sky1p, Ptk1p, and Ptk2p to
increase sensitivity to LiCl depends on the integrity of
PPZ1 but not of ENA1.
*
Corresponding author. Mailing address: Department of
Molecular Genetics, The Weizmann Institute of Science, Rehovot 76100, Israel. Phone: 972-8-9342745. Fax: 972-8-9466599 or 972-8-9344108. E-mail: chaim.kahana{at}weizmann.ac.il.
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