BRCA1-dependent ubiquitination of gamma-tubulin regulates centrosome number.
Proper centrosome duplication and spindle formation are crucial for prevention of chromosomal instability, and BRCA1 plays a role in this process. In this study, transient inhibition of BRCA1 function in cell lines derived from mammary tissue caused rapid amplification and fragmentation of centrosomes. Cell lines tested that were derived from nonmammary tissues did not amplify the centrosome number in this transient assay. We tested whether BRCA1 and its binding partner, BARD1, ubiquitinate centrosome proteins. Results showed that centrosome components, including gamma-tubulin, are ubiquitinated by BRCA1/BARD1 in vitro. The in vitro ubiquitination of gamma-tubulin was specific, and function of the carboxy terminus was necessary for this reaction; truncated BRCA1 did not ubiquitinate gamma-tubulin. BRCA1/BARD1 ubiquitinated lysines 48 and 344 of gamma-tubulin in vitro, and expression in cells of gamma-tubulin K48R caused a marked amplification of centrosomes. This result supports the notion that the modification of these lysines in living cells is critical in the maintenance of centrosome number. One of the key problems in understanding the biology of BRCA1 has been the identification of a specific target of BRCA1/BARD1 ubiquitination and its effect on mammary cell biology. The results of this study identify a ubiquitination target and suggest a biological impact important in the etiology of breast cancer.
SciCrunch is a data sharing and display platform. Anyone can create a custom portal where they can select searchable subsets of hundreds of data sources, brand their web pages and create their community. SciCrunch will push data updates automatically to all portals on a weekly basis. User communities can also add their own data to scicrunch, however this is not currently a free service.