Hetero-oligomerization does not compromise 'gain of function' of tumor-derived p53 mutants.
Tumor-derived p53 mutants activate transcription from promoters of various growth-related genes. We tested whether this transactivation function of the mutant protein is sufficient to induce tumorigenesis ('gain of function'). Tumor-derived mutant p53-281G transactivates the promoters of human epidermal growth factor receptor (EGFR) and human multiple drug resistance gene (MDR-1). To determine whether the C-terminal domain functions only as an oligomerization domain in mutant p53-mediated transactivation, we have replaced the tetramerization domain of p53 by a heterologous tetramerization domain; although this mutant protein formed tetramers in solution, it failed to transactivate significantly. Therefore, for successful mutant p53-mediated transactivation, sequences near the C-terminus of mutant p53 are required to perform functions in addition to tetramerization. We also demonstrate that co-expression of a deletion mutant of p53 (p53 del 1-293), which retains the p53 oligomerization domain, inhibits this transactivation. p53 del 1-293 co-immunoprecipitates with p53-281G suggesting that hetero-oligomers of p53-281G and p53 del 1-293 are defective in transactivation. We also show that a cell line stably transfected with p53-281G expresses higher levels of endogenous NF-kappaB and proliferating cell nuclear antigen (PCNA) compared to that transfected with vector alone. On co-expression, p53 del 1-293 lowered the levels of NF-kappaB and PCNA in p53-281G-expressing cells. However, on co-expression, p53 del 1-293 did not inhibit the tumorigenicity and colony forming ability of p53-281G expressing cells. Our earlier work showed that a deletion of the C-terminal sequences of p53-281G overlapping the oligomerization domain obliterates 'gain of function'. Taken together, the above information suggests that the C-terminal sequences have some critical role in 'gain of function' in addition to transactivation.
Deb
Debabrita
D
Department of Biochemistry and Molecular Biophysics, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia, VA 23298, USA.
Scian
Mariano
M
Roth
Katherine E
KE
Li
Wei
W
Keiger
Jane
J
Chakraborti
Abhay Sankar
AS
Deb
Swati Palit
SP
Deb
Sumitra
S
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D003114:Colony-Forming Units Assay; D016158:Genes, p53; D006801:Humans; D046911:Macromolecular Substances; D016296:Mutagenesis; D020411:Oligonucleotide Array Sequence Analysis; D012516:Osteosarcoma; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry / Q000235:genetics*
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D016159:Tumor Suppressor Protein p53; D015500:Chloramphenicol O-Acetyltransferase