A cell sizer network involving Cln3 and Far1 controls entrance into S phase in the mitotic cycle of budding yeast.

Saccharomyces cerevisiae must reach a carbon source-modulated critical cell size, protein content per cell at the onset of DNA replication (Ps), in order to enter S phase. Cells grown in glucose are larger than cells grown in ethanol. Here, we show that an increased level of the cyclin-dependent inhibitor Far1 ...
increases cell size, whereas far1 Delta cells start bud emergence and DNA replication at a smaller size than wild type. Cln3 Delta, far1 Delta, and strains overexpressing Far1 do not delay budding during an ethanol glucose shift-up as wild type does. Together, these findings indicate that Cln3 has to overcome Far1 to trigger Cln-Cdc28 activation, which then turns on SBF- and MBF-dependent transcription. We show that a second threshold is required together with the Cln3/Far1 threshold for carbon source modulation of Ps. A new molecular network accounting for the setting of Ps is proposed.
Mesh Terms:
CDC28 Protein Kinase, S cerevisiae, Cell Cycle Proteins, Cell Size, Cyclin-Dependent Kinase Inhibitor Proteins, Cyclins, DNA Replication, Ethanol, Glucose, Mitosis, Repressor Proteins, S Phase, Saccharomyces cerevisiae Proteins, Saccharomycetales, Transcription, Genetic
J. Cell Biol.
Date: Nov. 08, 2004
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