Structural Biochemistry/brca1

BRCA1 is a gene that produces a protein called breast cancer type 1 susceptibility protein that is ultimately responsible for repairing DNA. BRCA1 is expressed in breast cell tissues as well as other tissues. It helps repair damaged DNA or kill any cells if it cannot be repaired. If BRCA1 itself is damaged, DNA cannot be repaired and this leads to an increase risk for cancer. The BRCA1 protein works with other tumor suppressors, DNA damage sensors, and signal transducers to form a large protein complex called BRCA1 – associated genome surveillance complex (BASC). The BRCA1 protein is also associated with RNA polymerase II through the c-terminus as well as interacts with the histone deacetylase. The BRCA1 protein plays an important role in DNA repair of double stranded breaks, transcription, transcriptional regulation, and ubiquitination.

Structure
The BRCA1 protein has four main protein domains, the Znd C3hc4- ring domain, serine domain, and two BRCT domains that consist of BRCA1 and BRCA2. These domains encode for 27% if the BRCA1 protein BRCA1 gene is located on the log arm of the 17th chromosome at region 2 on band 1 and base pairs 38, 429551 to base pair 38,551,283.

Function
BRCA1 repairs breaks in the double strands in DNA. The double helixes are continuously breaking in DNA by cross-linking, transcription, and translation. There are many ways to repair a broken DNA. One-way is to replace the broken DNA with a sister chromatid. This is called homologous recombination. BRCA1 utilizes a sister chromatid from a homologous chromosome to form the same chromosome as a template. BRCA1 reacts with several different proteins to repair the broken gene. BRCA1 protein interacts with RAD51 during DNA repair. The BRCA2 protein, which has a similar function as BRCA1 also, interacts with RAD51 by influencing DNA damage repair.

Mutations
Mutations in the BRCA1 gene can lead to breast cancer or hereditary breast-ovarian cancer syndrome. Women with mutations in their BRCA1 or BRCA2 gene have about a 60% risk of developing breast cancer at 90 and an increased risk of ovarian cancer is seen in about 55% of women These mutations can be as simple as one change in a base pair. However, sometimes-large portions of the BRACA1 gene in DNA are rearranged. These rearrangements can be from a deletion, duplication, or an addition of unwanted base pairs. A mutated BRCA1 gene makes a protein that is abnormally short and therefore does not work properly and cannot repair the double-helix strand in DNA. Mutations in the BRCA1 gene can also lead to an increase risk for ovarian, fallopian tube, and prostate cancer.