The cAMP pathway and a specific PKA, Tpk1, transmit the glucose
signal that inhibits meiosis in Saccharomyces cerevisiae
.
Yona Kassir (1), Sabine Martin (1), Galit Shenhar (1), Hans
Kuntzel (2)
(1) Biology, Technion , Technion City, Haifa, 32000, Israel;
(2) Max-Planck-Institute for experimental Medicine, Hermann-Rein-Strasse
3, D-37075 Gottingen, Germany
The choice between meiosis and alternative developmental pathways in
budding yeast depends on the availability of glucose, which inhibits the
transcription and activity of the master regulator of meiosis, Ime1. We
focus on a specific element in IME1 promoter, IREu, which serves
as a repression element in the presence of glucose, and as an activation
element in its absence. We show that deletions of the glucose receptor,
GPR1, its coupled Galfa protein, GPA2, the small G-protein, RAS2, the SH3 domain of the GDP/GTP exchange factor,
CDC25, a temperature-sensitive mutation in Cdc25 catalytic
domain, as well as deletion of TPK1, one of the three genes
encoding the catalytic domain of PKA, result in an increase in the UAS
activity of IREu. On the other hand, addition of cAMP and deletions of
the non-essential N-terminal domain of CDC25, or BCY1, PKA
regulatory subunit, result in a decrease in activity of IREu. We show
physical associations between the N-terminal domain of Cdc25 and Gpr1,
as well as between the C-terminal catalytic domain of Cdc25 and Gpa2.
The results we show, as well as previous results, identifying Sok2 and
Msn2/4 as the proteins that bind to IREu, regulating its function,
establish a complete signal pathway.
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