Up-regulation of NFkappaB-responsive gene expression by DeltaNp73alpha in p53 null cells.
Transactivation domain (TAD)-truncated p73, DeltaNp73, associates with p53, resulting in suppression of p53's functions. Using p53 null cell lines, we examined whether or not DeltaNp73 can regulate gene expression in a p53-independent manner. When DeltaNp73alpha was co-transfected with a luciferase reporter plasmid with various enhancer elements, NFkappaB-responsive luciferase gene expression was selectively up-regulated by DeltaNp73alpha, but not by other p73-isoforms with TAD and DeltaNp73beta. Deletion of the TAD endowed p73alpha with the ability to enhance the responsive gene's expression, but deletion of the N-terminal proline-rich domain (PRD) rendered the TAD-deleted p73alpha inactive. Considering the inability of DeltaNp73beta, which is the C-terminus-truncated form of DeltaNp73alpha, to function, these results indicate that both the PRD and C-terminus are necessary for DeltaNp73alpha to can activate NFkappaB-responsive luciferase expression. Over-expression of p53 suppressed the TAD-truncated p73alpha-mediated luciferase expression, suggesting that p53 interferes with the TAD-truncated p73alpha-mediated activation of NFkappaB. Inhibitors for NFkappaB activation reduced the TAD-truncated p73alpha-dependent NFkappaB-responsive gene expression, indicating that TAD-truncated p73alpha activates NFkappaB as does TNFalpha. In addition to the results obtained in the reporter gene assay, TAD-truncated p73alpha stimulated the translocation of NFkappaB to the nucleus and the expression of an endogenous NFkappaB-responsive gene, Bcl-XL. Taken together, these results demonstrate that TAD-truncated p73alpha can activate NFkappaB.
Tanaka
Yasuharu
Y
Department of Biochemistry, Nara Medical University, Shijo-Cho 840, Kashihara, Nara 634-8521, Japan. ytanaka@naramed-u.ac.jp
Ota
Katsuya
K
Kameoka
Masanori
M
Itaya
Asako
A
Yoshihara
Koichiro
K
D021581:Active Transport, Cell Nucleus / Q000235:genetics; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D009154:Mutation / Q000235:genetics; D016328:NF-kappa B / Q000235:genetics*; D009369:Neoplasms / Q000235:genetics* / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D010446:Peptide Fragments / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D050436:Regulatory Elements, Transcriptional / Q000235:genetics; D015533:Transcriptional Activation / Q000235:genetics; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000235:genetics*; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism; D015854:Up-Regulation / Q000235:genetics*; D051020:bcl-X Protein / Q000235:genetics
D004268:DNA-Binding Proteins; D016328:NF-kappa B; D009687:Nuclear Proteins; D010446:Peptide Fragments; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D051020:bcl-X Protein