BRCA2

Overview


BRCA2 (Breast Cancer Type 2 susceptibility protein) is a human gene that is involved in the repair of chromosomal damage and belongs to a class of genes known as tumor suppressor genes. Tumor suppressor genes regulate the cycle of cell division by keeping cells from growing and dividing too rapidly or in an uncontrolled way.

Although the structures of the BRCA1 and BRCA2 genes are very different, their functions appear to be similar. The proteins made by both genes are essential for repairing damaged DNA. The BRCA2 protein binds to and regulates the protein produced by the RAD51 gene to fix breaks in DNA. These breaks can be caused by natural and medical radiation or other environmental exposures, but also occur when chromosomes exchange genetic material during a special type of cell division that creates sperm and eggs (meiosis). The BRCA1 protein also interacts with the RAD51 protein. By repairing DNA, these three proteins play a role in maintaining the stability of the human genome.

Like BRCA1, BRCA2 probably regulates the activity of other genes and plays a critical role in embryo development.

The BRCA2 gene is located on the long (q) arm of chromosome 13 at position 12.3, from base pair 31,787,616 to base pair 31,871,804.

Related conditions
Certain variations of the BRCA2 gene cause an increased risk for breast cancer. Researchers have identified about 450 mutations in the BRCA2 gene, many of which cause an increased risk of cancer. BRCA2 mutations are usually insertions or deletions of a small number of DNA base pairs (the building material of chromosomes) in the gene. As a result of these mutations, the protein product of the BRCA2 gene is abnormally short and does not function properly. Researchers believe that the defective BRCA2 protein is unable to help fix mutations that occur in other genes. As a result, mutations build up and can cause cells to divide in an uncontrolled way and form a tumor.

People who have two mutated copies of the BRCA2 gene have one type of Fanconi anemia. This condition is caused by extremely reduced levels of the BRCA2 protein in cells, which allows the accumulation of damaged DNA. Patients with Fanconi anemia are prone to several types of leukemia (a type of blood cell cancer); solid tumors, particularly of the head, neck, skin, and reproductive organs; and bone marrow suppression (reduced blood cell production that leads to anemia).

In addition to breast cancer in men and women, mutations in BRCA2 also lead to an increased risk of ovarian, prostate, and pancreatic cancers. In particular, mutations in the central part of the gene have been associated with a higher risk of ovarian cancer and a lower risk of prostate cancer than mutations in other parts of the gene. Several other types of cancer have also been seen in families with BRCA2 mutations.

Discovery of BRCA2
The BRCA2 gene was discovered in 1995 by Professor Michael Stratton and Dr Richard Wooster (Institute of Cancer Research, UK). The Wellcome Trust Sanger Institute (Hinxton, Cambs, UK) collaborated with Stratton and Wooster to isolate the gene. In honour of this discovery and collaboration, the Wellcome Trust has participated in the construction of a cycle path between Addenbrooke's Hospital site in Cambridge and the nearby village of Great Shelford. It is decorated with over 10,000 lines of 4 colours representing the nucleotide sequence of BRCA2. It makes-up part of the National Cycle Network route 11, and can be seen from the Cambridge-London Liverpool Street train.