By Dr Ananya Mandal, MD
The BRCA1 gene is a genetic sequence that is located on the long arm of chromosome 17 at the 17q21 position. The gene spans around 100 kilobases and codes for a protein containing 1863 amino acids. This is a large protein complex known of as the BRCA1-associated genome surveillance complex (BASC).
Tumor suppressor actions in cancer prevention
BRCA1 is essentially a tumor suppressor gene. It acts mainly by preventing abnormal proliferation and alteration of the cells. The gene helps in deoxyribonucleic acid (DNA) repair and keeps cellular proliferation in check.
The body is made up of trillions of living cells. These cells grow, divide, and die in an orderly fashion. This process is tightly regulated and controlled by the DNA machinery within each cell. During adulthood, most cells divide only to replace worn-out or dying cells or to repair injuries.
Cancer cells arise from cells in which the DNA machinery inside the nucleus is damaged. When a cell's DNA is damaged, the cell usually either repairs the damage or dies. In the case of cancer however, the cell continues to grow and forms new, abnormal cells.
In addition, the cells can also invade other tissues, a property that normal cells do not possess. So, in the case of cancer cells, the damaged DNA is not repaired, the cell does not die, and instead gives rise to more abnormal cells that all have the same defective DNA as the original cancer cell.
As a tumor supressor gene, the BRCA1 gene prevents tDNA from being damaged and forming tumor DNA. The gene usually repairs breaks in double-stranded DNA, regulates transcription by controlling the expression of genes in response to stress, and terminates the cell cycle. When the cell cycle is stopped, cells with altered DNA are killed if repair of the DNA is unsuccesful.
BRCA1 gene mutation
Mutations or alterations that affect the BRCA1 gene are linked to familial breast and ovarian cancer syndromes. The BRCA1 protein is also called RING finger protein 53 and has two known domains - Zinc finger, C3HC4 type (RING finger) and BRCA1 C Terminus (BRCT) domain.
Reviewed by Sally Robertson, BSc