A novel mechanism whereby BRCA1/1a/1b fine tunes the dynamic complex interplay between SUMO-dependent/independent activities of Ubc9 on E2-induced ERα activation/repression and degradation in breast cancer cells

  • Authors:
    • J. Xu
    • T. Watkins
    • A. Reddy
    • E. S.P. Reddy
    • V. N. Rao
  • View Affiliations

  • Published online on: April 1, 2009     https://doi.org/10.3892/ijo_00000220
  • Pages: 939-949
Metrics: Total Views: 0 (Spandidos Publications: | PMC Statistics: )
Total PDF Downloads: 0 (Spandidos Publications: | PMC Statistics: )


Abstract

BRCA1 dysfunction is associated with hormone-responsive cancers. We have identified a consensus SUMO modification site in the amino-terminal region of BRCA1/1a/1b proteins and the mutation in this potential SUMO acceptor site (K 109 to R) impaired their ability to bind and repress ligand-dependent ERα transcriptional activity in breast cancer cells. Furthermore, we have found SUMO E2-conjugating enzyme Ubc9 to bind BRCA1 proteins. We have mapped BRCA1 [within amino acids (aa) 1-182] as the minimum domain that is sufficient for in vitro binding to Ubc9 as well as for regulating ERα activity. BRCA1 Mutant #1 (K109 to R) was impaired in its ability to both bind, as well as modulate Ubc9 mediated SUMO-dependent/independent E2-induced ERα transcriptional activity in breast cancer cells. Similarly, BRCA1 cancer-predisposing mutation (61Cys-Gly) abrogated the ability to both bind Ubc9 as well as inhibit ERα activity suggesting physiological significance. Addition of BRCA1 but not Mutant #1 to E2-induced ERα in the presence of SUMO-1 and Ubc9 resulted in the degradation of ERα suggesting BRCA1 to be a putative SUMO-1 and Ubc9-dependent E3 ubiquitin ligase for ERα. This is the first report demonstrating the participation of Ubc9 in BRCA1 E3 ubiquitin ligase mediated degradation of ERα. These results suggest a novel function for BRCA1 in regulating the dynamic cycles of SUMO and ubiquitin modifications required for ERα turn over and deregulation of this molecular switch due to lack of BRCA1 results in ERα-negative/positive breast cancers. This study will help in designing novel BRCA1 function-based targeted treatment for breast cancers.

Related Articles

Journal Cover

April 2009
Volume 34 Issue 4

Print ISSN: 1019-6439
Online ISSN:1791-2423

Sign up for eToc alerts

Recommend to Library

Copy and paste a formatted citation
x
APA
Xu, J., Watkins, T., Reddy, A., Reddy, E.S., & Rao, V.N. (2009). A novel mechanism whereby BRCA1/1a/1b fine tunes the dynamic complex interplay between SUMO-dependent/independent activities of Ubc9 on E2-induced ERα activation/repression and degradation in breast cancer cells. International Journal of Oncology, 34, 939-949. https://doi.org/10.3892/ijo_00000220
MLA
Xu, J., Watkins, T., Reddy, A., Reddy, E. S., Rao, V. N."A novel mechanism whereby BRCA1/1a/1b fine tunes the dynamic complex interplay between SUMO-dependent/independent activities of Ubc9 on E2-induced ERα activation/repression and degradation in breast cancer cells". International Journal of Oncology 34.4 (2009): 939-949.
Chicago
Xu, J., Watkins, T., Reddy, A., Reddy, E. S., Rao, V. N."A novel mechanism whereby BRCA1/1a/1b fine tunes the dynamic complex interplay between SUMO-dependent/independent activities of Ubc9 on E2-induced ERα activation/repression and degradation in breast cancer cells". International Journal of Oncology 34, no. 4 (2009): 939-949. https://doi.org/10.3892/ijo_00000220