Coordination of cell growth with cell division: G1 cyclin regulation of nitrogen metabolism

Abstract

How cell growth and metabolism are coupled with cell division is largely unknown. We examined budding yeast cells growing under continuous culture conditions, and found that cell growth requirements were not limited to the G1 phase of the cell cycle. Furthermore, the duration of cell cycle phases was different between nitrogen and glucose-limited cultures grown at the same rate. Loss of G1 cyclins, or inactivation of the cyclin-dependent kinase Cdc28p, reduced the activity of glutamate synthase, Glt1p, a key nitrogen assimilation enzyme. Jem1p, a DnaJ-type chaperone whose expression peaks at START, mediates the G1 cyclin-dependent control of Glt1p. Thus, our results establish a molecular link between START completion and control of nitrogen metabolism.