Major component of the cell cycle transcription factor complex MBF (MCB binding factor, also known as DSC1), that controls G1-S phase specific gene expression. Involved in the control of rRNA production, via interaction with pol5. May be involved in the transcriptional regulation of the cdc22 and cdt1 genes. In fission yeast, two genes, cdc10 and cdc2, are required for the cell cycle control called start, the point early in the G1 phase at which cells become committed to the mitotic cycle. DSC1 contains cdc10 and sct1/res1. Interacts with pol5.