E3 ligase activity of BRCA1 is not essential for mammalian cell viability or homology-directed repair of double-strand DNA breaks Journal Article
| Authors: | Reid, L. J.; Shakya, R.; Modi, A. P.; Lokshin, M.; Cheng, J. T.; Jasin, M.; Baer, R.; Ludwig, T. |
| Article Title: | E3 ligase activity of BRCA1 is not essential for mammalian cell viability or homology-directed repair of double-strand DNA breaks |
| Abstract: | Hereditary cases of breast and ovarian cancer are often attributed to germ-line mutations of the BRCA1 tumor suppressor gene. Although BRCA1 is involved in diverse cellular processes, its role in the maintenance of genomic integrity may be a key component of its tumor suppression activity. The protein encoded by BRCA1 interacts in vivo with the related BARD1 protein to form a heterodimeric complex that acts as a ubiquitin E3 ligase. Because the enzymatic activity of the BRCA1/BARD1 heterodimer is conserved over a broad phylogenetic range, it is thought to be critical for the central functions of BRCA1. To test this hypothesis, we have generated isogenic clones of embryonic stem cells that do or do not express an enzymatically proficient Brca1 polypeptide. Surprisingly, cells lacking the ubiquitin ligase activity of BRCA1 are viable and do not accumulate spontaneous cytogenetic rearrangements. Gene targeting efficiencies are modestly reduced in these cells, and chromosomal rearrangements arise at elevated rates in response to genotoxic stress. Nonetheless, cells lacking Brca1 enzymatic activity are not hypersensitive to the DNA cross-linking agent mitomycin C. They also form Rad51 focus in response to ionizing radiation and repair chromosome breaks by homologous recombination at wild-type levels. These results indicate that key aspects of BRCA1 function in genome maintenance, including its role in homology-directed repair of double-strand DNA breaks, do not depend on the E3 ligase activity of BRCA1. © 2008 by The National Academy of Sciences of the USA. |
| Keywords: | controlled study; nonhuman; ovarian neoplasms; animal cell; mammalia; animals; mice; cell viability; homologous recombination; gene targeting; dna repair; breast cancer; gene expression; embryonic stem cell; protein assembly; cell line; gene function; enzyme activity; breast neoplasms; brca1 protein; molecular cloning; chromosome aberration; recombination, genetic; genomic instability; tumor suppressor proteins; dna breaks, double-stranded; radiation, ionizing; mitomycin c; dna double-strand break repair; chromosome breakage; chromosome rearrangement; double stranded dna break; embryonic stem cells; chromosome aberrations; mitomycin; ubiquitin protein ligase e3; chromosome analysis; ubiquitin-protein ligases; gene knockdown techniques; rad51 protein; genotoxicity; rad51 recombinase; mammary neoplasms, animal; cross linking; cross-linking reagents; e3 ubiquitin ligase; brca1/bard1 heterodimer |
| Journal Title: | Proceedings of the National Academy of Sciences of the United States of America |
| Volume: | 105 |
| Issue: | 52 |
| ISSN: | 0027-8424 |
| Publisher: | National Academy of Sciences |
| Date Published: | 2008-12-30 |
| Start Page: | 20876 |
| End Page: | 20881 |
| Language: | English |
| DOI: | 10.1073/pnas.0811203106 |
| PUBMED: | 19088202 |
| PROVIDER: | scopus |
| PMCID: | PMC2603436 |
| DOI/URL: | |
| Notes: | --- - "Cited By (since 1996): 30" - "Export Date: 17 November 2011" - "CODEN: PNASA" - "Source: Scopus" |
