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Cyclin-dependent protein kinases have a central role in cell cycle regulation. In Saccharomyces cerevisiae, Cdc28 kinase and the G1 cyclins Cln1, 2 and 3 are required for DNA replication, duplication of the spindle pole body and bud emergence. These three independent processes occur simultaneously in late G1 when the cells reach a critical size, an event known as Start. At least one of the three Clns is necessary for Start. Cln3 is believed to activate Cln1 and Cln2, which can then stimulate their own accumulation by means of a positive feedback loop. They (or Cln3) also activate another pair of cyclins, Clb5 and 6, involved in initiating S phase. Little is known about the role of Clns in spindle pole body duplication and budding. We report here the isolation of a gene (CLA2/BUD2/ERC25) that codes for a homologue of mammalian Ras-associated GTPase-activating proteins (GAPs) and is necessary for budding only in cln1 cln2 cells. This suggests that Cln1 and Cln2 may have a direct role in bud formation.


Journal article



Publication Date





5277 - 5286


Amino Acid Sequence, Base Sequence, Cell Cycle, Cloning, Molecular, Cyclins, Fungal Proteins, GTP Phosphohydrolase Activators, GTP Phosphohydrolases, GTPase-Activating Proteins, Genes, Lethal, Humans, Infant, Newborn, Molecular Sequence Data, Proteins, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Sequence Alignment, Sequence Homology, Amino Acid, ras GTPase-Activating Proteins