What type of substance makes up cell cycle regulators?

Cell cycle regulators are primarily composed of proteins. These proteins include cyclins, which are essential for the progression through different phases of the cell cycle, and cyclin-dependent kinases (CDKs), which are enzymes that, when activated by cyclins, facilitate the cell cycle's transition. Additionally, various checkpoint proteins and tumor suppressors, such as p53 and Rb, also play critical roles in regulating the cell cycle. Together, these substances ensure proper cell division and prevent uncontrolled cell growth.