RESUMO
The p53-family member p73 plays a role in various cellular signaling pathways during development and growth control and it can have tumor suppressor properties. Several isoforms of p73 exist with considerable differences in their function. Whereas the functions of the N-terminal isoforms (TA and ΔNp73) and their opposing pro- and antiapoptotic roles have become evident, the functional differences of the distinct C-terminal splice forms of TAp73 have remained unclear. Here, we characterized the global genomic binding sites for TAp73α and TAp73ß by chromatin immunoprecipitation sequencing as well as the transcriptional responses by performing RNA sequencing. We identified a specific p73 consensus binding motif and found a strong enrichment of AP1 motifs in close proximity to binding sites for TAp73α. These AP1 motif-containing target genes are selectively upregulated by TAp73α, while their mRNA expression is repressed upon TAp73ß induction. We show that their expression is dependent on endogenous c-Jun and that recruitment of c-Jun to the respective AP1 sites was impaired upon TAp73ß expression, in part due to downregulation of c-Jun. Several of these AP1-site containing TAp73α-induced genes impinge on apoptosis induction, suggesting an underlying molecular mechanism for the observed functional differences between TAp73α and TAp73ß.
Assuntos
Apoptose/genética , Proteínas de Ligação a DNA/metabolismo , Proteínas Nucleares/metabolismo , Proteínas Proto-Oncogênicas c-jun/metabolismo , Ativação Transcricional , Proteínas Supressoras de Tumor/metabolismo , Sítios de Ligação , Linhagem Celular , Sobrevivência Celular , Proteínas de Ligação a DNA/química , Complexos Endossomais de Distribuição Requeridos para Transporte/genética , Humanos , Proteína Acessória do Receptor de Interleucina-1/genética , Ubiquitina-Proteína Ligases Nedd4 , Proteínas Nucleares/química , Isoformas de Proteínas/química , Isoformas de Proteínas/metabolismo , Estrutura Terciária de Proteína , Elementos Reguladores de Transcrição , Fator de Transcrição AP-1/metabolismo , Proteína Tumoral p73 , Proteínas Supressoras de Tumor/química , Ubiquitina-Proteína Ligases/genéticaRESUMO
Leukemia caused by retroviral insertional mutagenesis after stem cell gene transfer has been reported in several experimental animals and in patients treated for X-linked severe combined immunodeficiency. Here, we analyzed whether gene transfer into mature T cells bears the same genotoxic risk. To address this issue in an experimental "worst case scenario," we transduced mature T cells and hematopoietic progenitor cells from C57BL/6 (Ly5.1) donor mice with high copy numbers of gamma retroviral vectors encoding the potent T-cell oncogenes LMO2, TCL1, or DeltaTrkA, a constitutively active mutant of TrkA. After transplantation into RAG-1-deficient recipients (Ly5.2), animals that received stem cell transplants developed T-cell lymphoma/leukemia for all investigated oncogenes with a characteristic phenotype and after characteristic latency periods. Ligation-mediated polymerase chain reaction analysis revealed monoclonality or oligoclonality of the malignancies. In striking contrast, none of the mice that received T-cell transplants transduced with the same vectors developed leukemia/lymphoma despite persistence of gene-modified cells. Thus, our data provide direct evidence that mature T cells are less prone to transformation than hematopoietic progenitor cells.
