What Are the Functions of P53?

P53 is also known as Protein 53 or Tumour Protein 53. It is a human gene that appears in the 17th chromosome and is used to treat human cancers. It is called p53 because its molecular mass is the 53 kilo dilation of cell proteins. It is also called the "guardian of the genome" because of its ability to prevent genome mutation.

History

• P53 was discovered in 1979 by Arnold Levine of Princeton University, David Lane of Dundee University and William Old of Sloane-Kettering Memorial Hospital. It was thought that within the body p53 was the target of SV40 virus, which induces tumours, but by 1989 its ability to suppress tumours was revealed. In 1993 Science magazine voted p53 the 'Molecule of the Year'.

Mechanisms

• P53 plays an important role in cell cycle and apoptosis, or cell death. Defective p53 allows abnormal cells to multiply and is found in 50 percent of human cancers. In a normal situation p53 levels are low. Cell damage and other stress signals cause p53 levels to increase. The increased p53 has 3 functions. It stops growth, (so stops the replication of damaged cells), activates proteins that repair damaged DNA; or kills the damaged cells.

Role in Disease

• In a healthy person, p53 is continually produced and degraded within the cell and has a continuing ability to suppress tumours. When p53 is damaged, its ability to suppress tumours is reduced. Chemicals, radiation and viruses can all damage p53 and sometimes p53 is lacking. A genetic disease, called Li-Fraumeni disease occurs when individuals inherit only 1 functioning copy of the p53 gene. This condition causes tumours to appear in early adulthood.

Therapeutic Use

• Injecting p53 into p53 deficient cells has been shown to kill cancer cells. In the 50 percent of human cancers that are caused by defective p53, restoring its proper function is a major step in curing the cancer. A cancer treatment that is still being researched uses adenovirus. This virus secretes proteins into host cells which it then compels to replicate. When the cells replicate, so does the viral DNA. However, adenovirus can be modified to include p53 and when these modified cells replicate they should lyse (or disintegrate) cancer cells. To date this therapy only works in conjunction with chemotherapy.