Effects of partner proteins on BCA2 RING ligase activity

BMC Cancer

Research Article

Angelika Burger¹  Judit Zubovits²  Yutaka Amemiya³  Wenyi Yang³  Martin Yaffe³  Arun K Seth⁴  Stephanie Bacopulos⁴ 

[1] Barbara Ann Karmanos Cancer Institute and Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA;Department of Anatomic Pathology, Sunnybrook Health Sciences Centre, Toronto, ON, Canada;Sunnybrook Research Institute, S-238, 2075 Bayview Avenue, M4N 3M5, Toronto, ON, Canada;Sunnybrook Research Institute, S-238, 2075 Bayview Avenue, M4N 3M5, Toronto, ON, Canada;Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada;

关键词: HEK293T Cell;    Partner Protein;    Mammary Epithelial Cell Line;    133A Mutant;    Negative Nodal Status;   

DOI  :  10.1186/1471-2407-12-63

 received in 2011-09-30, accepted in 2012-02-08,  发布年份 2012

来源: Springer

【 摘 要 】

BackgroundBCA2 is an E3 ligase linked with hormone responsive breast cancers. We have demonstrated previously that the RING E3 ligase BCA2 has autoubiquitination activity and is a very unstable protein. Previously, only Rab7, tetherin, ubiquitin and UBC9 were known to directly interact with BCA2.MethodsHere, additional BCA2 binding proteins were found using yeast two-hybrid and bacterial-II-hybrid screening techniques with Human breast and HeLa cDNA libraries. Co-expression of these proteins was analyzed through IHC of TMAs. Investigation of the molecular interactions and effects were examined through a series of in vivo and in vitro assays.ResultsTen unique BCA2 interacting proteins were identified, two of which were hHR23a and 14-3-3sigma. Both hHR23a and 14-3-3sigma are co-expressed with BCA2 in breast cancer cell lines and patient breast tumors (n = 105). hHR23a and BCA2 expression was significantly correlated (P = < 0.0001 and P = 0.0113) in both nucleus and cytoplasm. BCA2 expression showed a statistically significant correlation with tumor grade. High cytoplasmic hHR23a trended towards negative nodal status. Binding to BCA2 by hHR23a and 14-3-3sigma was confirmed in vitro using tagged partner proteins and BCA2. hHR23a and 14-3-3sigma effect the autoubiquitination and auto-degradation activity of BCA2. Ubiquitination of hHR23a-bound BCA2 was found to be dramatically lower than that of free BCA2, suggesting that hHR23a promotes the stabilization of BCA2 by inactivating its autoubiquitination activity, without degradation of hHR23a. On the other hand, phosphorylated BCA2 protein is stabilized by interaction with 14-3-3sigma both with and without proteasome inhibitor MG-132 suggesting that BCA2 is regulated by multiple degradation pathways.ConclusionsThe interaction between BCA2 and hHR23a in breast cancer cells stabilizes BCA2. High expression of BCA2 is correlated with grade in breast cancer, suggesting regulation of this E3 ligase is important to cancer progression.

【 授权许可】

Unknown   
© Bacopulos et al; BioMed Central Ltd. 2012. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.