Question

8.      How does Rb act to regulate the cell cycle?

Answer 1

Rb is a gene that regulates the protien also known as retinoblastomal protien(pRb). The primary function of Rb in cell cycle is to prevent cell overgrowth by inhibiting cell cycle until the cell is ready to divide. Rb restrict DNA replication in cell the preventing the transition from G1 to S phase. Thus it is responsible for G1 checkpoint. The pRb protien(Rb/p105, p107 and Rb2/p130, collectively referred to as ‘pocket proteins’) prevents the gene transcription required for transition to S-phase by remodeling chromatin structure. Hence it is a vital protien required for controlled growth of cell.Loss of pRb functions may induce cell cycle deregulation and so lead to a malignant phenotype. Inactivation of pRB due to chromosomal mutations is one of the principal reasons for retinoblastoma tumor.