Max Animations

Tumor-suppressor genes generally encode proteins that in one way or another inhibit cell proliferation. Loss-offunction mutations in one or more of these “brakes” contribute to the development of many cancers. Five broad classes of proteins are generally recognized as being encoded by tumor-suppressor genes:

• Intracellular proteins that regulate or inhibit progression through a specific stage of the cell cycle (e.g., p16 and Rb)
• Receptors or signal transducers for secreted hormones or developmental signals that inhibit cell proliferation (e.g., TGF , the hedgehog receptor patched)
• Checkpoint-control proteins that arrest the cell cycle if DNA is damaged or chromosomes are abnormal (e.g., p53)
• Proteins that promote apoptosis
• Enzymes that participate in DNA repair