EXPRESSION OF DNA-REPLICATION GENES IN THE YEAST-CELL CYCLE

In recent years, numerous studies using a wide variety of systems have clearly established some of the fundamental components of eukaryotic cell-division control. These include p34cdc2 protein kinases (henceforth referred to as p34) and closely related proteins (p33cdc2), and the members of the cyclin gene family which, through interaction with the p34 (and p33) kinases, regulate transitions from one stage of the cell cycle to the next. The function of these proteins in the cell cycle has been conserved to the extent that p34 protein kinase and cyclin genes are, in some cases, interchangeable between organisms. Despite the tremendous insight that studies on p34 and the cyclins have provided, many questions remain about the details of the molecular events which allow these proteins to govern cell division. One question of particular interest concerns the means by which p34 interaction with G1 phase cyclins promotes G1 to S phase transition in the cell cycle. This is of primary importance since entry into the cell cycle is regulated, for most cells, by passage from G1 (or G0) into S phase. Recent findings in the yeast Saccharomyces cerevisiae point to a potential link between the p34/G1 cyclin protein kinase complex and the regulation of DNA replication genes during the cell cycle. This paper reviews studies dealing with the transcriptional control of DNA replication genes in yeast and also briefly discusses the potential role of G1 cyclins in this process. A similar review of this subject has also been given by Johnston and Lowndes (1992).