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Uncovering residues that regulate cyclin D1 proteasomal degradation
Author(s) -
Feng Qing,
Sekula David,
Freemantle Sarah J.,
Dmitrovsky Ethan
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a1130
Subject(s) - cyclin d1 , cyclin d , cyclin b , ubiquitin , cyclin a2 , proteasome , lysine , microbiology and biotechnology , cancer research , cyclin a , biochemistry , cyclin dependent kinase , chemistry , biology , cell cycle , amino acid , gene
Study objective Our prior work highlighted cyclin D1 proteasomal degradation as a cancer chemopreventive mechanism of retinoids and other agents. To better understand this, cyclin D1 ubiquitination mechanisms were investigated. Methods Eighteen lysines present in the cyclin D1 were individually or multiply mutated and then transfected into human bronchial epithelial cells to evaluate stabilities following pharmacological and physiological treatments. Results Specific individual lysine mutations inhibited cyclin D1 degradation. Multiple lysine mutations from positions 33 to 123 prominently inhibited this degradation and polyubiquitination of cyclin D1. These mutations greatly extended cyclin D1 half‐life. Mutation of the N‐terminus (but not C‐terminus) also stabilized cyclin D1. These results identified cyclin D1 lysine residues from amino acids 33 to 123 and the N‐terminus as playing critical roles in cyclin D1 ubiquitination. Interestingly, the multiple lysine mutations preferentially localized cyclin D1 to the nucleus, directly implicating subcellular translocalization in regulating cyclin D1 degradation. Conclusions Specific residues regulate cyclin D1 stability and are novel pharmacological targets for proteasome‐dependent degradation. This work was supported by the National Institutes of Health and National Cancer Institute grants RO1‐CA087546, RO1‐CA111422, and RO1‐CA62275 as well as by the Samuel Waxman Cancer Research Foundation and the Oracle Giving Fund.