We are interested in the mechanism of cell cycle commitment and cell cycle-regulated transcription. In particular, we have been investigating the mechanism of cell cycle regulation by two G1-specific transcription factors, SBF and MBF, that control a massive burst of gene expression at Start (see diagram below). There are three broad controls over SBF/MBF activity: the binding of SBF to its target site in early G1, the activation of SBF at Start and the dissociation of SBF from DNA after S-phase. In recent years, we have explored all three facets of SBF/MBF regulation and we are continuing to study these key regulators. For example, we are currently examining Whi5, a G1 transcriptional repressor which acts by binding SBF and MBF and we are exploring the steps involved in the inhibition of Whi5 by Cdc28 and Pho85. We are also using functional genomics to identify additional G1 transcriptional regulators and we are studying the physical interactions between these putative G1 transcriptional regulators and SBF or MBF. Finally, we are employing high throughput promoter-based reporter screens to identify novel proteins that directly or indirectly control the expression of genes during specific phases of the cell cycle.