P53 hot-spot mutants are resistant to ubiquitin-independent degradation by increased binding to NAD(P)H:quinone oxidoreductase 1.

Abstract

Proteasomal degradation of p53 is mediated by two alternative pathways that are either dependent or independent of both Mdm2 and ubiquitin. The ubiquitin-independent pathway is regulated by NAD(P)H: quinone oxidoreductase 1 (NQO1) that stabilizes p53. The NQO1 inhibitor dicoumarol induces ubiquitin-independent p53 degradation. We now show that, like dicoumarol, several other coumarin and flavone inhibitors of NQO1 activity, which compete with NAD(P)H for binding to NQO1, induced ubiquitin-independent p53 degradation and inhibited wild-type p53-mediated apoptosis. Although wild-type p53 and several p53 mutants were sensitive to dicoumarol-induced degradation, the most frequent "hot-spot" p53 mutants in human cancer, R175H, R248H, and R273H, were resistant to dicoumarol-induced degradation, but remained sensitive to Mdm2-ubiquitin-mediated degradation. The two alternative pathways for p53 degradation thus have different p53 structural requirements. Further mutational analysis showed that arginines at positions 175 and 248 were essential for dicoumarol-induced p53 degradation. NQO1 bound to wild-type p53 and dicoumarol, which induced a conformational change in NQO1, inhibited this binding. Compared with wild-type p53, the hot-spot p53 mutants showed increased binding to NQO1, which can explain their resistance to dicoumarol-induced degradation. NQO1 thus has an important role in stabilizing hot-spot p53 mutant proteins in human cancer.

• Authors: Gad Asher, Joseph Lotem, Peter Tsvetkov, Veronica Reiss, Leo Sachs, Yosef Shaul
• Journal: Proceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A) Vol. 100 Issue 25 Pg. 15065-70 (Dec 09 2003) ISSN: 0027-8424 [Print] United States
• PMID: 14634213 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Multienzyme Complexes
• Nuclear Proteins
• Proto-Oncogene Proteins
• Tumor Suppressor Protein p53
• Ubiquitin
• Dicumarol
• Arginine
• NAD(P)H Dehydrogenase (Quinone)
• NQO1 protein, human
• MDM2 protein, human
• Mdm2 protein, mouse
• Proto-Oncogene Proteins c-mdm2
• Cysteine Endopeptidases
• Proteasome Endopeptidase Complex

Topics

• Animals
• Apoptosis
• Arginine (chemistry)
• Cell Line
• Cell Line, Tumor
• Cell Survival
• Cysteine Endopeptidases (metabolism)
• DNA Mutational Analysis
• Dicumarol (pharmacology)
• Dose-Response Relationship, Drug
• Genes, p53
• Humans
• Immunoblotting
• Mice
• Multienzyme Complexes (metabolism)
• Mutation
• NAD(P)H Dehydrogenase (Quinone) (chemistry, metabolism)
• Nuclear Proteins
• Plasmids (metabolism)
• Precipitin Tests
• Proteasome Endopeptidase Complex
• Protein Binding
• Protein Conformation
• Proto-Oncogene Proteins (metabolism)
• Proto-Oncogene Proteins c-mdm2
• Transfection
• Tumor Suppressor Protein p53 (metabolism, physiology)
• Ubiquitin (metabolism)