Research Paper Volume 3, Issue 5 pp 515—532
Mutations in the BRCT binding site of BRCA1 result in hyper-recombination
- 1 Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA 23298, USA
- 2 Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, VA 23298, USA
- 3 Department of Pathology, Virginia Commonwealth University, Richmond, VA 23298, USA
- 4 Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, VA 23298, USA
- 5 Department Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA 23298, USA
- 6 Massey Cancer Center, Virginia Commonwealth University, Richmond, VA 23298, USA
- 7 Department of Radiation Oncology, The Methodist Hospital, Houston, TX 77030, USA
Received: April 27, 2011 Accepted: May 5, 2011 Published: May 8, 2011
https://doi.org/10.18632/aging.100325How to Cite
Abstract
We introduced a K1702M mutation in the BRCA1 BRCT domain known to prevent the binding of proteins harboring pS-X-X-F motifs such as Abraxas-RAP80, BRIP1, and CtIP. Surprisingly, rather than impairing homologous recombination repair (HRR), expression of K1702M resulted in hyper-recombination coinciding with an accumulation of cells in S-G2 and no effect on nonhomologous end-joining. These cells also showed increased RAD51 and RPA nuclear staining. More pronounced effects were seen with a naturally occurring BRCT mutant (M1775R) that also produced elevated levels of ssDNA, in part co-localizing with RPA, in line with excessive DNA resection. M1775R induced unusual, thread-like promyelocytic leukemia (PML) nuclear bodies and clustered RPA foci rather than the typical juxtaposed RPA-PML foci seen with wild-type BRCA1. Interestingly, K1702M hyper-recombination diminished with a second mutation in the BRCA1 RING domain (I26A) known to reduce BRCA1 ubiquitin-ligase activity. These in vitro findings correlated with elevated nuclear RAD51 and RPA staining of breast cancer tissue from a patient with the M1775R mutation. Altogether, the disruption of BRCA1 (BRCT)-pS-X-X-F protein binding results in ubiquitination-dependent hyper-recombination via excessive DNA resection and the appearance of atypical PML-NBs. Thus, certain BRCA1 mutations that cause hyper-recombination instead of reduced DSB repair might lead to breast cancer.