Abstract
The cyclin-dependent kinase (CDK) inhibitor p27Kip1 (p27) is an important regulator of cell cycle progression controlling the transition from G to S-phase. Low p27 levels or accelerated p27 degradation correlate with excessive cell proliferation and poor prognosis in several forms of cancer. Phosphorylation of p27 at Thr187 by cyclin E-CDK2 is required to initiate the ubiquitination-proteasomal degradation of p27. Protecting p27 from ubiquitin-mediated proteasomal degradation may increase its potential in cancer gene therapy. Here we constructed a non-phosphorylatable, proteolysis-resistant p27 mutant containing a Thr187-to-Ala substitution (T187A) which is not degraded by ubiquitin-mediated proteasome pathway, and compared its effects on cell growth, cell-cycle control, and apoptosis with those of wild-type p27. In muristerone A-inducible cell lines overexpressing wild-type or mutant p27, the p27 mutant was more resistant to proteolysis in vivo and more potent in inducing cell-cycle arrest and other growth-inhibitory effects such as apoptosis. Transduction of p27(T187A) in breast cancer cells with a doxycycline-regulated adenovirus led to greater inhibition of proliferation, more extensive apoptosis, with a markedly reduced protein levels of cyclin E and increased accumulation of cyclin D1, compared with wild-type p27. These findings support the potential effectiveness of a degradation-resistant form of p27 in breast cancer gene therapy.
Original language | English (US) |
---|---|
Pages (from-to) | 3932-3940 |
Number of pages | 9 |
Journal | FEBS Letters |
Volume | 579 |
Issue number | 18 |
DOIs | |
State | Published - Jul 18 2005 |
Keywords
- Apoptosis
- Breast cancer
- Proteolysis
- T187A
- p27
ASJC Scopus subject areas
- Biophysics
- Structural Biology
- Biochemistry
- Molecular Biology
- Genetics
- Cell Biology