Inhibition of G1 cyclin activity by the Ras/cAMP pathway in yeast.
In the yeast Saccharomyces cerevisiae, commitment to cell division (Start) requires growth to a critical cell size. The G1 cyclins Cln1, Cln2 and Cln3 activate the Cdc28 protein kinase and are rate-limiting activators of Start. When glucose is added to cells growing in a poor carbon source, the critical cell size required for Start is reset from a small to a large size. In yeast, glucose acts through Ras proteins to stimulate adenylyl cyclase, activating the three cyclic AMP-dependent protein kinases Tpk1, Tpk2 and Tpk3 (refs 8, 9). We find that stimulation of the Ras/cAMP pathway represses expression of CLN1, CLN2 and co-regulated genes, inhibiting Start. This helps explain the increase in critical size when cells are shifted from poor to rich medium. This connection between the molecules controlling growth (Ras/cAMP) and those controlling division (cyclins) helps explain how division is co-ordinated with growth.
Tokiwa
G
G
Cold Spring Harbor Laboratory, New York 11724.
Tyers
M
M
Volpe
T
T
Futcher
B
B
D002455:Cell Division / Q000235:genetics / Q000502:physiology; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D016213:Cyclins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism*; D016193:G1 Phase / Q000235:genetics / Q000502:physiology; D015966:Gene Expression Regulation, Fungal; D005947:Glucose / Q000378:metabolism; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D018631:ras Proteins
D016213:Cyclins; D005656:Fungal Proteins; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D018631:ras Proteins; D005947:Glucose