Part of a complex involved in cell-cycle-dependent transcription. SWI4 and SWI6 are required for formation of the cell-cycle box factor-DNA complex. The repeated element in the upstream region of HO (5'-CACGAAAA-3') is called the cell cycle box (CCB). Component of the transcription complex MCB-binding factor (MBF) composed of SWI6 and MBP1. Component of the transcription complex SCB-binding factor (SBF) composed of SWI6 and SWI4. Interacts with MSA1 and STB1. Phosphorylated by CDC28 and dephosphorylated by CDC14. Present with 3340 molecules/cell in log phase SD medium.