title: Mutational analysis of Mdm2 C-terminal tail suggests an evolutionarily conserved role of its length in Mdm2 activity toward p53 and indicates structural differences between Mdm2 homodimers and Mdm2/MdmX heterodimers.
abstract: Mdm2 can mediate p53 ubiquitylation and degradation either in the form of the Mdm2 homodimer or Mdm2/MdmX heterodimer. The ubiquitin ligase activity of these complexes resides mainly in their respective RING finger domains and also requires adjacent C-terminal tails. So far, structural studies have failed to show significant differences between Mdm2 RING homodimers and Mdm2/MdmX RING heterodimers. Here, we report that not only the primary amino acid sequence, but also the length of the C-terminal tail of Mdm2 is highly conserved through evolution and plays an important role in Mdm2 activity toward p53. Mdm2 mutants with extended C termini do not ubiquitylate p53 despite being capable of forming Mdm2 homodimers through both RING-acidic domain and RING-RING interactions. All extended mutants also retained the ability to interact with MdmX, and this interaction led to reactivation of their E3 ubiquitin ligase activity. In contrast, only a subset of extended Mdm2 mutants was activated by the interaction with Mdm2 RING domain, suggesting that Mdm2 homodimers and Mdm2/MdmX heterodimers may not be structurally and functionally fully equivalent.
authors.affiliation: Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic.
authors.forename: Pavlina
authors.initials: P
authors.lastname: Dolezelova
authors.forename: Katerina
authors.initials: K
authors.lastname: Cetkovska
authors.forename: Karen H
authors.initials: KH
authors.lastname: Vousden
authors.forename: Stjepan
authors.initials: S
authors.lastname: Uldrijan
mesh_terms: D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D004252:DNA Mutational Analysis; D019281:Dimerization; D019143:Evolution, Molecular; D057809:HEK293 Cells; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051736:Proto-Oncogene Proteins c-mdm2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D051034:Inhibitor of Apoptosis Proteins; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2