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EMBO J

Title:		Roles and regulation of Cln-Cdc28 kinases at the start of the cell cycle of Saccharomyces cerevisiae
Author(s):		Dirick L; Bohm T; Nasmyth K;
Address:		"Research Institute of Molecular Pathology, Vienna, Austria"
Journal Title:		EMBO J
Year:		1995
Volume:		14
Issue:		19
Page Number:		4803 - 4813
DOI:		10.1002/j.1460-2075.1995.tb00162.x
ISSN/ISBN:		0261-4189 (Print) 1460-2075 (Electronic) 0261-4189 (Linking)
Abstract:		"In budding yeast G1 cells increase in cell mass until they reach a critical cell size, at which point (called Start) they enter S phase, bud and duplicate their spindle pole bodies. Activation of the Cdc28 protein kinase by G1-specific cyclins Cln1, Cln2 or Cln3 is necessary for all three Start events. Transcriptional activation of CLN1 and CLN2 by SBF and MBF transcription factors also requires an active Cln-Cdc28 kinase and it has therefore been proposed that the sudden accumulation of CLN1 and CLN2 transcripts during late G1 occurs via a positive feedback loop. We report that whereas Cln1 and Cln2 are required for the punctual execution of most, if not all, other Start-related events, they are not required for the punctual activation of SBF- or MBF-driven transcription. Cln3, on the other hand, is essential. By turning off cyclin B proteolysis and turning on proteolysis of the cyclin B-Cdc28 inhibitor p40SIC1, Cln1 and Cln2 kinases activate cyclin B-Cdc28 kinases and thereby trigger S phase. Thus the accumulation of Cln1 and Cln2 kinases which starts the yeast cell cycle is set in motion by prior activation of SBF- and MBF-mediated transcription by Cln3-Cdc28 kinase. This dissection of regulatory events during late G1 demands a rethinking of Start as a single process that causes cells to be committed to the mitotic cell cycle"
Keywords:		"CDC28 Protein Kinase, S cerevisiae/*physiology *Cyclin B Cyclin-Dependent Kinase Inhibitor Proteins Cyclins/genetics/metabolism/*physiology DNA Replication/physiology Drug Resistance, Microbial Fungal Proteins/metabolism/*physiology G1 Phase/*physiology G;"
Notes:		"MedlineDirick, L Bohm, T Nasmyth, K eng Research Support, Non-U.S. Gov't England 1995/10/02 EMBO J. 1995 Oct 2; 14(19):4803-13. doi: 10.1002/j.1460-2075.1995.tb00162.x"