科研之友
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摘要
Background: p63 is a member of the p53 transcription factor family. p63 is expressed from two promoters resulting in proteins with opposite functions: the transcriptionally active TAp63 and the dominant-negative Delta Np63. Similar to p53, the TAp63 isoforms induce cell cycle arrest and apoptosis. The Delta Np63 isoforms are dominant-negative variants opposing the activities of p53, TAp63 and TAp73. To avoid unnecessary cell death accompanied by proper response to stress, the expression of the p53 family members must be tightly regulated. NAD(P)H quinone oxidoreductase (NQO1) has recently been shown to interact with and inhibit the degradation of p53. Due to the structural similarities between p53 and p63, we were interested in studying the ability of wild-type and polymorphic, inactive NQO1 to interact with and stabilize p63. We focused on TAp63 gamma, as it is the most potent transcription activator and it is expected to have a role in tumor suppression.
Principal Findings: We show that TAp63 gamma can be degraded by the 20S proteasomes. Wild-type but not polymorphic, inactive NQO1 physically interacts with TAp63 gamma, stabilizes it and protects it from this degradation. NQO1-mediated TAp63 gamma stabilization was especially prominent under stress. Accordingly, we found that downregulation of NQO1 inhibits TAp63 gamma-dependant p21 upregulation and TAp63 gamma-induced growth arrest stimulated by doxorubicin.
Conclusions/Significance: Our report is the first to identify this new mechanism demonstrating a physical and functional relationship between NQO1 and the most potent p63 isoform, TAp63 gamma. These findings appoint a direct role for NQO1 in the regulation of TAp63 gamma expression, especially following stress and may therefore have clinical implications for tumor development and therapy.
- 出版日期2010-6-30
