Tp53 Gene Location On The Chromosone

Published Date: 02 Nov 2017

TP53 gene location on the chromosone

The protein is found in the nucleus of the cell and is bound to the DNA. When working correctly the protein regulates cell division so that tumours don’t form. It also has another very important role. Let’s say for instance that the cells have been exposed to radiation or burns to the extent that DNA has been damaged. The protein has the very important role of deciding whether the DNA can be repaired or whether the cell has to go through the process of apoptosis (programmed cell death). This example alone shows the importance of this gene working correctly so that transcription works correctly to produce the proper protein and so begs the question "How does this relate to breast cancer?" Well there are a few answers to that question. One result of a defective TP53 gene is Li-Fraumeni syndrome. Any cell that has this type of defective TP53 gene has a far greater risk of contracting cancer "Individuals with LFS have up to a 50% chance of developing cancer by age 40 and a 90% chance to develop cancer by age 60. Breast cancer appears to be the greatest risk for women. However, less than 1% of all breast cancer is thought to be related to LFS." [1] Another cause of breast cancer by a defective TP53 gene is caused by the somatic mutations which account for "20% to 30% of all breast cancer cases" [2] . The usual cause is that an abnormal amino acid is produced in the protein chain which makes the protein ineffective and therefore causes the cell to grow and divide erratically. The same symptoms can be noticed if the TP53 gene is absent in a cell.

PTEN

Phosphatase and tensin homolog (PTEN) is a very important gene that produces a protein found in nearly all tissue. The PTEN protein is an enzyme that modifies fats and other proteins by removing phosphate groups.

PTEN gene location on the chromosome

When working correctly the enzyme, created by the PTEN gene, is involved in the chemical pathway which signals apoptosis (programmed cell death). PTEN is also thought to help in the control of cell adhesion, cell migration and angiogenesis. Once again the question of how this gene relates to breast cancer. All of the roles of the enzyme created by this gene add up to a key tumour suppressor as all are involved in cell proliferation in some way. The main cancerous danger of this gene is caused by somatic mutations that change the gene, this results in a defective enzyme being produced. This defective enzyme is not able to control cell proliferation as it should and therefore cancerous cells can be allowed to reproduce and grow at an uncontrollable rate.

STK11

Serine/threonine kinase 11 (STK11) gene creates a protein that acts as a tumour suppressor.

STK11 gene location on the chromosome

The enzyme stops the cell from reproducing irregularly and is also another link in the promotion of the process known as apoptosis (programmed cell death). Another useful role by this enzyme when the gene is working correctly is the polarisation effects it has on cells e.g. it assists in the orientation of cells in tissue. The protein also controls how much energy is used by the cell. All these are key control elements in tumour suppression. Mutations in this gene cause Peutz-Jeghers syndrome. Over 140 different mutations [3] of the STK11 gene have been reported to cause this syndrome. Mutations usually create a shorter non functioning version of the enzyme and studies show that when the enzyme isn’t functioning properly the cell divides to quickly and polyps are formed which sometimes develop into cancerous tumours. With the defective enzyme comes as a far larger risk of breast cancer. Only a small percentage of breast cancers are actually related to Peutz-Jeghers syndrome which are usually inherited. Its even rarer for breast cancer to be caused by somatic mutations in this gene but it has happened. Cells tend to uncontrollably divide which in turn leads to malignant growths.

CDH1

Cadherin 1, E-cadherin (epithelial) (CDH1) is responsible for the production of the protein E-cadherin.

CDH1 gene location on the chromosome

Cadherins are proteins that bind cells together (cell adhesion) to form tissues. They are calcium dependent which means they require the presence of calcium to perform properly. In addition to cell adhesion E-cadherins have some very important roles which include the transmition of chemical messengers from cell to cell, control of cell movement and control of selected genetic behaviour. Studies suggest that CDH1 is a tumour suppressor gene which helps regulate cell proliferation and stop cancerous tumours from growing. Also because cadherins help cells stick together it is thought that they stop cancerous cells from breaking free and entering the blood stream which limits the spread of cancer to other tissues (metastisizing). There is an increased risk of breast cancer when the CDH1 gene is mutated. Inherited mutations of the CDH1 gene increase the risk of lobular breast cancer that begins in the mammary glands. Somatic mutations of this gene are common but so are damages to the DNA that calls upon the gene. It is thought that the genetic mutations lead to uncontrollable division and growth of the cells. Also the lack of E-cadherins, through errors in its synthesis, can lead to cancerous cells metastisizing to other parts of the body.