Retinoblastoma is a fast growing cancer which manifests in the eye’s retina. Retina is a tissue that detects light. Retinoblastoma protein is a tumor suppressor protein. This protein is usually impaired in different types of cancer. It is abbreviated as Rb or pRb. The most important function of retinoblastoma protein is to prevent unrestrained cell growth. It inhibits the progression of the cell cycle until a cell is ready for cell division. It also recruits many chromatin remodelling enzymes like acetylases and methylases.
Retinoblastoma protein is a part of the pocket protein family. The members of this family have a dock to bind to the functional group of other proteins. Oncogenic proteins can bind and inactivate the retinoblastoma protein. This can lead to cancer. For example, oncogenic protein is produced by those cells which are infected by high-risk types of human papillomaviruses.
Genetics Of Retinoblastoma Protein
The protein is encoded by the RB1 gene which is located on 13q14.1-q14.2 in humans. The development of retinoblastoma cancer occurs when both the alleles of the gene are mutated at an earlier stage of life. This results in inactivation of the retinoblastoma protein. Hence, the name Rb was coined.
There are two forms of retinoblastoma cancer:
- bilateral, familial form
- unilateral, sporadic form
Patients who suffer from the bilateral form of cancer are 6 times more likely to develop other types of cancer later in life. This revealed the fact that mutated form of Rb could be inherited. In most mammals, RB1 orthologs have been identified. The complete genome data are available for this orthologs.
Suppression Of Cell Cycle
Retinoblastoma protein prevents the cell from replicating damaged DNA. It halts the cell cycle while its progressing through G1 (first gap phase) into S (synthesis phase). It binds and inhibits the transcription factors of the E2F family.
