Question

What is the role of the retinoblastoma protein in cell-cycle regulation? Is the retinoblastoma gene a tumor-suppressor gene or an oncogene?

Short answer

Answer: The retinoblastoma gene is a tumor-suppressor gene.

Step-by-step solution

The retinoblastoma protein plays a vital role in cell-cycle regulation, specifically during the transition from the G1 phase to the S phase. In its active (hypophosphorylated) form, the Rb protein binds with the transcription factor E2F, inhibiting its function and preventing the expression of S-phase-promoting genes. This helps to control cell proliferation and prevents unregulated cell division. The Rb protein becomes inactivated when it gets phosphorylated by specific cyclin-dependent kinases (CDKs). This causes Rb to release E2F, enabling the progression from the G1 phase to the S phase of the cell cycle. #Step 2: Determine if the retinoblastoma gene is a tumor-suppressor gene or an oncogene#

The retinoblastoma gene, also known as the RB1 gene, encodes the Rb protein. Since the Rb protein functions in regulating cell-cycle progression by inhibiting the activity of transcription factors responsible for promoting cell division, its loss or inactivation can lead to uncontrolled cell proliferation. This characteristic makes the retinoblastoma gene a tumor-suppressor gene, as its normal function is to suppress the development of tumors by regulating the cell cycle. Mutations or loss of function in the RB1 gene can lead to various cancers, including retinoblastoma, a childhood cancer of the eye. An oncogene, on the other hand, is a gene that, when mutated or overexpressed, contributes to the formation or progression of cancer by promoting unregulated cell division. So based on the role of the retinoblastoma protein in cell-cycle regulation and its function in suppressing tumors: The retinoblastoma gene is a tumor-suppressor gene.