Final Answer:
- True (T): The overexpression of MPF (Maturation-Promoting Factor) activity can lead to uncontrolled growth in cancer.
- True (T): A nonfunctional RB (Retinoblastoma) protein can contribute to uncontrolled growth in cancer.
- True (T): The overexpression of cyclin can lead to uncontrolled growth in cancer.
- True (T): A nonfunctional E2F protein can contribute to uncontrolled growth in cancer.
Step-by-step explanation:
1. **Overexpression of MPF Activity (T):** Maturation-Promoting Factor (MPF) is a complex of cyclin and cyclin-dependent kinase (CDK) that regulates cell cycle transitions. Overexpression of MPF activity, particularly an excess of cyclin-CDK complexes, can lead to uncontrolled cell division, a hallmark of cancer. This overexpression may result in cells bypassing normal regulatory checkpoints, promoting continuous proliferation.
2. **Nonfunctional RB Protein (T):** The Retinoblastoma (RB) protein is a tumor suppressor that regulates the cell cycle by inhibiting the activity of E2F transcription factors. When RB is nonfunctional, it cannot effectively restrain E2F, allowing for uncontrolled progression through the cell cycle. This loss of regulation can contribute to the development of cancer.
3. **Overexpression of Cyclin (T):** Cyclins are regulatory proteins that control the activation of CDKs. Overexpression of cyclins can lead to excessive activation of CDKs, resulting in uncontrolled cell cycle progression and potential tumorigenesis. Cyclin overexpression disrupts the balance of the cell cycle, promoting continuous cell division.
4. **Nonfunctional E2F Protein (T):** E2F transcription factors regulate the expression of genes involved in cell cycle progression. A nonfunctional E2F protein can disrupt the normal control of gene expression, leading to uncontrolled cell proliferation. Dysregulation of E2F is frequently observed in cancer, emphasizing its role in controlling cell cycle progression.