Question

1. What is p53? What is pRB? How are they involved in cancer? What are there pathways and why do cancer cells need to lose both P53 and pRB?

Answer 1

Ans:

p53 is a gene that codes for a protein which regulates the cell cycle. It functions as a tumor suppression. P53 is also referred as the guardian of the genome. It play a vital role in preventing genome mutation.

The name of this gene is coded p53 because of its molecular mass which is 53 kilodalton fraction of cell proteins.

It was first identified in 1979 by Arnold Levine, David Lane and William. It was initially thought to be an oncogene but later was revealed as tumor suppressor gene in 1989.

pRB is also a tumor supressor gene which plays a significant role in control of cell cycle. It was first identified in a malignant tumor of the retina known as retinoblastoma.

Involvement in cancer:

Both these protein plays important role in cell cycle control and apoptosis. The defective p53 and pRB gene causes abnormal cells to proliferate and hence result in cancer.

These genes are low in normal cells but DNA damage and other stress signals increases level .It causes growth arrest in progression of cell cycle, preventing replication of damaged DNA. During the growth arrest, these protein gets activate the transcription of proteins involves in DNA repair. Apoptosis is the last step to avoid proliferation of cells containing abnormal DNA. Hence, preventing proliferation of cancerous cells.

they act on apoptotic pathways and restrict proliferation of tumor cells.

The cancer cells need to lose these because these genes are cancer supressor and their presence restrict multiplication of cancerous cells by restricting faulty gene multipication at specific time of cell cycle. there absence will severely affect the oncogene supression.

these mutations are reported in almost 50% of cancer genes.