WHAT IS p53?

This protein is one of the most important protein in eukaryotic cells. If this protein is suppressed in any cell or is not functioning properly then normal cells may turn into malignant cells and form tumor or cancer. This protein is used to stop the cell cycle if thee is any damage or mutation in the DNA of the cell.

DAMAGED DNA

We usually get this protein from p53 gene. p53 protein is produced in very small amount and is always present in ones cell. When everything inside the cell is completely fine then this protein is highly unstable, there half life is also very less. So, they are being produced and gets destroyed very fast and the process continues. 

If any DNA gets damaged they become stable and there production rises very fast. these proteins are transcription regulatory proteins and hence they are used to make mRNA. They sit on promote WAF1 and produces WAF1 mRNA and p21 protein is produced after translation. 

During cell cycle, cyclin and CDK helps cell to move further and divide, but in case if there is any problem with DNA or the cell, then this p21 protein binds with the cyclin - CDK complex and doesn't allow the cells to move further. If the problem can be fixed the cell cycle is paused and if the problem cannot be fixed apoptosis takes place. 

Sometimes these p53 protein are somehow suppressed then these are not that active and causes the cancerous cells.

ROUGH IDEA OF HOW A p53 HELPS IN STOPPING THE DAMAGED OR MUTATED CELL