Processes Regulating the G
/S transition in mammalian cells. Scheme of the G1 to S transition of the mammalian cell cycle drawn with Cell Designer. Two compartments are considered, cytoplasm and nucleus. The scheme follows the systems biology graphical notation (SBGN); each component is associated with a red number and each reaction is associated with a black number (Additional file 1). In the gray box a set of reactions which are not explicitly considered for the model.