Interaction of p53 with MDM2 is independent of E6 and does not mediate wild type transformation suppressor function.
Using a new series of p53 mutants targeting the conserved regions we have analysed the relationship of various activities of the protein. Mdm-2 and human papillomavirus (HPV) E6, two proteins which interact with and abrogate p53 function, were shown to bind independently. Deletion of the conserved regions of the protein in which most of the naturally occurring mutations are found (boxes II-V) abrogated transcriptional activity and the ability to interact with E6, supporting the importance of this DNA binding domain to these activities. Nevertheless, these mutants retained the ability to interact with mdm2. One mutant, deleted of all the C-terminal sequences, showed loss of mdm2 binding, E6 binding and transcriptional activity. More subtle mutations within the C-terminus of the protein, including alterations of the cdc2 and CKII phosphorylation sites, had no effect on the transcriptional trans-activation, mdm-2 or E6 binding functions, indicating that phosphorylation of these sites is not essential for these activities. Deletion of conserved box I sequences abolished the interaction with mdm-2 without loss of transcriptional activation or transformation suppressor activity, suggesting that mdm-2 is not a downstream effector of p53 function.
Marston
N J
NJ
Ludwig Institute for Cancer Research, St Mary's Hospital Medical School, London, UK.
Crook
T
T
Vousden
K H
KH
D016203:CDC2 Protein Kinase / Q000502:physiology; D047388:Casein Kinases; D002471:Cell Transformation, Neoplastic; D009154:Mutation; D009363:Neoplasm Proteins / Q000502:physiology*; D009687:Nuclear Proteins; D009856:Oncogene Proteins, Viral / Q000502:physiology*; D010766:Phosphorylation; D011494:Protein Kinases / Q000502:physiology; D011518:Proto-Oncogene Proteins; D051736:Proto-Oncogene Proteins c-mdm2; D012097:Repressor Proteins; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*
C068651:E6 protein, Human papillomavirus type 16; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D009856:Oncogene Proteins, Viral; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53; D051736:Proto-Oncogene Proteins c-mdm2; D011494:Protein Kinases; D047388:Casein Kinases; D016203:CDC2 Protein Kinase