Several hydrophobic amino acids in the p53 amino-terminal domain are required for transcriptional activation, binding to mdm-2 and the adenovirus 5 E1B 55-kD protein.
The p53 tumor suppressor gene product is a transcriptional activator that may be associated with its ability to suppress tumor cell growth. The acidic amino terminus of the p53 protein has been shown to contain this trans-activation activity as well as the domains for mdm-2 and adenovirus 5 E1B 55-kD protein binding. An extensive genetic analysis of this amino-terminal p53 domain has been undertaken using site-specific mutagenesis. The results demonstrate that the acidic residues in the amino terminus of p53 may contribute to, but are not critical for, this trans-activation activity. Rather, the hydrophobic amino acid residues Leu-22 and Trp-23 of human p53 are both required for trans-activation activity, binding to the adenovirus E1B 55-kD protein and the human mdm-2-p53 protein in vitro. In addition, hydrophobic residues Leu-14 and Phe-19 are crucial for the interactions between p53 and human mdm-2 (hdm-2). Hydrophobic residues Trp-23 and Pro-27 are also important for binding to the adenovirus 5 (Ad5) E1B 55-kD protein in vitro. These mutations have no impact on the ability of the p53 protein to bind to a p53-specific DNA element. These results suggest that 2-4 critical hydrophobic residues in the amino-terminal domain of the p53 protein interact with the transcriptional machinery of the cell resulting in transcriptional activation. These very same hydrophobic residues contact the hdm-2 and Ad5 E1B 55-kD oncogene products.
Lin
J
J
Department of Molecular Biology, Princeton University, New Jersey 08544-1014.
Chen
J
J
Elenbaas
B
B
Levine
A J
AJ
D017501:Adenovirus E1B Proteins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000502:physiology*; D016384:Consensus Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation / Q000502:physiology; D009363:Neoplasm Proteins / Q000378:metabolism*; D009687:Nuclear Proteins; D011089:Polydeoxyribonucleotides / Q000138:chemical synthesis / Q000378:metabolism; D011485:Protein Binding; D011518:Proto-Oncogene Proteins; D051736:Proto-Oncogene Proteins c-mdm2; D016385:TATA Box; D035181:TATA-Box Binding Protein; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation / Q000502:physiology*; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
D017501:Adenovirus E1B Proteins; D000596:Amino Acids; D004268:DNA-Binding Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011089:Polydeoxyribonucleotides; D011518:Proto-Oncogene Proteins; D035181:TATA-Box Binding Protein; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2