There are both stimulatory and inhibitory proteins that help to regulate the cell cycle. Name one stimulatory protein and one inhibitory protein. At what point in the cell cycle are these proteins active and what are their effects on the cell cycle and the fate of the cell? Im pretty sure that the stimulatory protein is cycline-dependent kinases, and the inhibitory protein is retinoblastoma proteins, but I don't know what point in the cell cycle these proteins are active and what are their effects on the cell cyle and the fate of the cell.