The Role of Ubiquitin-Mediated Proteolysis of Cyclin D in Breast Cancer
Abstract
Cyclin D is a positive regulator of the cell cycle and is found to be highly expressed in breast cancer cells. Cyclin D is post-transcriptionally regulated by the ubiquitin mediated protein degradation pathway. CDC34, a ubiquitin conjugating enzyme, and SCF (Skpl, Cullin, F-box, ring protein), a ubiquitin ligase, are postulated to be the specific E2 and E3 enzymes which target Cyclin D for ubiquitination. It is currently unclear how regulation of the CDC34-SCF complex may modulate Cyclin D proteolysis. In this regard, we have studied the regulation of CDC34 by phosphorylation and by CDC34-associated proteins as well as the interaction of CDC34 with the SCF components, Cull and Roci. Our results suggest that the carboxyl-terminal acidic tail domain of CDC34 does not appear to be critical for its interactions with Cull and Roci in an in vitro binding assay, while the role of CDC34 phosphorylation on Cull and Roci binding is still unclear. Currently, our work has focused on identifying the proteins which tightly associate with CDC34 and which are required for DNA replication initiation in Xenopus egg extracts. We are developing strategies to purify the CDC34- associated proteins from human HeLa cell extracts and from Xenopus egg extracts. We predict that these previously unidentified CDC34-associated proteins will play an important role in regulating the ubiquitination of cyclin D in vivo.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 2004
- Accession Number
- ADA425732
Entities
People
- Karen L. Block
Organizations
- University of Texas Health Science Center at San Antonio