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Mol. Cell. Biol., 01 1998, 433-441, Vol 18, No. 1
DI Jeoung, LJ Oehlen and FR Cross
The Saccharomyces cerevisiae cell cycle is arrested in G1 phase by the
mating factor pathway. Genetic evidence has suggested that the G1 cyclins
Cln1, Cln2, and Cln3 are targets of this pathway whose inhibition results
in G1 arrest. Inhibition of Cln1- and Cln2- associated kinase activity by
the mating factor pathway acting through Far1 has been described. Here we
report that Cln3-associated kinase activity is inhibited by mating factor
treatment, with dose response and timing consistent with involvement in
cell cycle arrest. No regulation of Cln3-associated kinase was observed in
a fus3 kss1 strain deficient in mating factor pathway mitogen-activated
protein (MAP) kinases. Inhibition occurs mainly at the level of specific
activity of Cln3-Cdc28 complexes. Inhibition of the C-terminally truncated
Cln3-1- associated kinase is not observed; such truncations were previously
identified genetically as causing resistance to mating factor-induced cell
cycle arrest. Regulation of Cln3-associated kinase specific activity by
mating factor treatment requires Far1. Overexpression of Far1 restores
inhibition of C-terminally truncated Cln3-1-associated kinase activity.
G2/M-arrested cells are unable to regulate Cln3- associated kinase,
possibly because of cell cycle regulation of Far1 abundance. Inhibition of
Cln3-associated kinase activity by the mating factor pathway may allow this
pathway to block the earliest step in normal cell cycle initiation, since
Cln3 functions as the most upstream G1-acting cyclin, activating
transcription of the G1 cyclins CLN1 and CLN2 as well as of the S-phase
cyclins CLB5 and CLB6.
Copyright © 1998, American Society for Microbiology
Cln3-associated kinase activity in Saccharomyces cerevisiae is regulated by the mating factor pathway
The Rockefeller University, New York, New York 10021, USA.
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