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PMID: 9475724 Published · ppublish English Journal Article Research Support, Non-U.S. Gov't

TOR2 is part of two related signaling pathways coordinating cell growth in Saccharomyces cerevisiae.

Genetics ·Vol. 148 ·No. 1 ·1998-01-00 ·Pages 99-112

Helliwell SB, Howald I, Barbet N, Hall MN

Abstract

The Saccharomyces cerevisiae genes TOR1 and TOR2 encode phosphatidylinositol kinase homologs. TOR2 has two essential functions. One function overlaps with TOR1 and mediates protein synthesis and cell cycle progression. The second essential function of TOR2 is unique to TOR2 and mediates the cell-cycle-dependent organization of the actin cytoskeleton. We have isolated temperature-sensitive mutants that are defective for either one or both of the two TOR2 functions. The three classes of mutants were as follows. Class A mutants, lacking only the TOR2-unique function, are defective in actin cytoskeleton organization and arrest within two to three generations as small-budded cells in the G2/M phase of the cell cycle. Class B mutants, lacking only the TOR-shared function, and class C mutants, lacking both functions, exhibit a rapid loss of protein synthesis and a G1 arrest within one generation. To define further the two functions of TOR2, we isolated multicopy suppressors that rescue the class A or B mutants. Overexpression of MSS4, PKC1, PLC1, RHO2, ROM2, or SUR1 suppressed the growth defect of a class A mutant. Surprisingly, overexpression of PLC1 and MSS4 also suppressed the growth defect of a class B mutant. These genes encode proteins that are involved in phosphoinositide metabolism and signaling. Thus, the two functions (readouts) of TOR2 appear to involve two related signaling pathways controlling cell growth.

MeSH Terms
Cell Cycle Proteins Cell Division/genetics Fungal Proteins/biosynthesis,physiology G1 Phase G2 Phase Genes, Fungal/genetics Metaphase Mutation Phosphatidylinositol 3-Kinases Phosphotransferases (Alcohol Group Acceptor)/physiology Saccharomyces cerevisiae/cytology,genetics,growth & development Saccharomyces cerevisiae Proteins Signal Transduction/genetics
Chemicals
Cell Cycle Proteins Fungal Proteins Saccharomyces cerevisiae Proteins Phosphotransferases (Alcohol Group Acceptor) TOR2 protein, S cerevisiae
Authors & Affiliations
4 authors, click to expand affiliations / ORCID
Helliwell S B
Department of Biochemistry, Biozentrum, University of Basel, Switzerland.
Howald I
Barbet N
Hall M N
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37 references, click to expand
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Article Info
Journal
Genetics
Abbr.
Genetics
ISSN
0016-6731
DOI
10.1093/genetics/148.1.99
Published
1998-01-00
Pages
99-112
Language
English
Region
United States
NLM ID
0374636
PMCID
PMC1459785
Subset
IM
External Links
PubMed source DOI: 10.1093/genetics/148.1.99 PMC Full Text View journal details
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