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Association of p19 ARF with Mdm2 inhibits ubiquitin ligase activity of Mdm2 for tumor suppressor p53
Author(s) -
Honda Reiko,
Yasuda Hideyo
Publication year - 1999
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/18.1.22
Subject(s) - mdm2 , ubiquitin ligase , ubiquitin , biology , dna ligase , phosphorylation , f box protein , dna damage , microbiology and biotechnology , mutant , biochemistry , dna , gene
We have demonstrated previously that the oncoprotein Mdm2 has a ubiquitin ligase activity for the tumor suppressor p53 protein. In the present study, we characterize this ubiquitin ligase activity of Mdm2. We first demonstrate the ubiquitination of several p53 point mutants and deletion mutants by Mdm2. The point mutants, which cannot bind to Mdm2, are not ubiquitinated by Mdm2. The ubiquitination of the C‐terminal deletion mutants, which contain so‐called Mdm2‐binding sites, is markedly decreased, compared with that of wild‐type p53. The binding of Mdm2 to p53 is essential for ubiquitination, but p53′s tertiary structure and/or C‐terminal region may also be important for this reaction. DNA‐dependent protein kinase is known to phosphorylate p53 on Mdm2‐binding sites, where DNA damage induces phosphorylation, and p53 phosphorylated by this kinase is not a good substrate for Mdm2. This suggests that DNA damage‐induced phosphorylation stabilizes p53 by inhibiting its ubiquitination by Mdm2. We further investigated whether the tumor suppressor p19 ARF affects the ubiquitin ligase activity of Mdm2 for p53. The activity of p19 ARF ‐bound Mdm2 was found to be lower than that of free Mdm2, suggesting that p19 ARF promotes the stabilization of p53 by inactivating Mdm2.