A general approach to the isolation of cell cycle-regulated genes in the budding yeast, Saccharomyces cerevisiae.

We describe a general approach to the isolation of cell cycle-dependently regulated transcripts in Saccharomyces cerevisiae. This approach is based on the physical identification of cell cycle-regulated transcripts by Northern hybridization using as probes yeast DNA isolated from an ordered S. cerevisiae genomic library. The purpose of this is twofold; first, to assess the importance of transcriptional regulation in cell cycle control; and second, to identify novel genes that may have important roles in the eukaryotic cell cycle. We report the isolation of two previously uncharacterized genes that are transcribed at points in the cell cycle to which specific transcriptional activation has not been assigned: namely, mitosis and early G1 phase. It is argued that these transcripts serve as important landmarks for cell cycle events that are not readily distinguished by either morphological or cytological criteria. The cell cycle-dependent transcription of the RNR1 and CLN1 genes is also described and the implications for cell cycle control, in G1, are discussed with reference to these two genes.