RESUMO
Interferon regulatory factor-1 (IRF-1) is an interferon-induced transcriptional activator that suppresses tumors by impeding cell proliferation. Recently, we demonstrated that the level of SUMOylated IRF-1 is elevated in tumor cells, and that SUMOylation of IRF-1 attenuates its tumor-suppressive function. Here we report that SUMOylated IRF-1 mimics IRF-2, an antagonistic repressor, and shows oncogenic potential. To demonstrate the role of SUMOylated IRF-1 in tumorigenesis, we used SUMO-IRF-1 recombinant protein. Stable expression of SUMO-IRF-1 in NIH3T3 cells resulted in focus formation and anchorage-independent growth in soft agar. Inoculation of SUMO-IRF-1-transfected cells into athymic nude mice resulted in tumor formation and infiltration of adipose tissues. Finally, we demonstrated that SUMO-IRF-1 transforms NIH3T3 cells in a dose-dependent manner suggesting that SUMOylated IRF-1 may act as an oncogenic protein in tumor cells.
Assuntos
Transformação Celular Neoplásica/metabolismo , Fator Regulador 1 de Interferon/metabolismo , Fator Regulador 2 de Interferon/metabolismo , Processamento de Proteína Pós-Traducional , Proteínas Modificadoras Pequenas Relacionadas à Ubiquitina/metabolismo , Animais , Linhagem Celular , Transformação Celular Neoplásica/genética , Transformação Celular Neoplásica/patologia , Humanos , Fator Regulador 1 de Interferon/genética , Fator Regulador 2 de Interferon/genética , Camundongos , Células NIH 3T3 , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , TransfecçãoRESUMO
The amphetamine derivative 3, 4-methylenedioxymethamphetamine (MDMA) has become a popular recreational drug, and has also been shown to cause serotonergic neurotoxicity. This report shows that MDMA impairs brain development in a whole mouse embryo culture. The results of quantitative real-time PCR analysis showed that autophagy-related protein 5 (Atg5) expression is elevated in mouse embryo and neuroblastoma cells after MDMA treatment. This elevated Atg5 expression interferes with the neuronal differentiation of neuroblastoma cells such as SH-SY5Y and PC12 cells. Thus, our results suggest that the use of MDMA during pregnancy may impair neuronal development via an induction of Atg5 expression.
Assuntos
Diferenciação Celular/efeitos dos fármacos , Proteínas Associadas aos Microtúbulos/genética , Proteínas Associadas aos Microtúbulos/metabolismo , N-Metil-3,4-Metilenodioxianfetamina/farmacologia , Neurônios/efeitos dos fármacos , Animais , Autofagia/efeitos dos fármacos , Proteína 5 Relacionada à Autofagia , Técnicas de Cultura Embrionária , Feminino , Desenvolvimento Fetal/efeitos dos fármacos , Humanos , Camundongos , Neuroblastoma/metabolismo , Neuroblastoma/patologia , Neurônios/metabolismo , Neurônios/patologia , Células PC12 , Gravidez , Proteínas/genética , Proteínas/metabolismo , Ratos , Tretinoína/metabolismoRESUMO
The Wnt/beta-catenin signaling pathway is activated during the malignant transformation of keratinocytes that originate from the human uterine cervix. Dkk1, 2 and 4 have been shown to modulate the Wnt-induced stabilization of the beta-catenin signaling pathway. However, the function of Dkk3 in this pathway is unknown. Comparison of the Dkk3 gene expression profiles in cervical cancer and normal cervical tissue by cDNA microarray and subsequent real-time PCR revealed that the Dkk3 gene is frequently downregulated in the cancer. Methylation studies showed that the promoter of Dkk3 was methylated in cervical cancer cell lines and 22 (31.4%) of 70 cervical cancer tissue specimens. This promoter methylation was associated with reduced expression of Dkk3 mRNA in the paired normal and tumor tissue samples. Further, the reintroduction of Dkk3 into HeLa cervical cancer cells resulted in reduced colony formation and retarded cell growth. The forced expression of Dkk3 markedly attenuated beta-catenin-responsive luciferase activity in a dose-dependent manner and decreased the beta-catenin levels. By utilizing a yeast two-hybrid screen, betaTrCP, a negative regulator of beta-catenin was identified as a novel Dkk3-interacting partner. Coexpression with betaTrCP synergistically enhanced the inhibitory function of Dkk3 on beta-catenin. The stable expression of Dkk3 blocks the nuclear translocation of beta-catenin, resulting in downregulation of its downstream targets (VEGF and cylcin D), whereas knockdown of Dkk3 abrogates this blocking. We conclude from our finding that Dkk3 is a negative regulator of beta-catenin and its downregulation contribute to an activation of the beta-catenin signaling pathway.
Assuntos
Regulação Neoplásica da Expressão Gênica , Peptídeos e Proteínas de Sinalização Intercelular/biossíntese , Neoplasias do Colo do Útero/metabolismo , beta Catenina/metabolismo , Transporte Ativo do Núcleo Celular , Proteínas Adaptadoras de Transdução de Sinal , Proliferação de Células , Transformação Celular Neoplásica , Quimiocinas , Regulação para Baixo , Feminino , Células HeLa , Humanos , Modelos Biológicos , Polimorfismo de Nucleotídeo Único , Regiões Promotoras Genéticas , Técnicas do Sistema de Duplo-HíbridoRESUMO
Nuclear Factor-kappa B (NF-kappaB) is a transcription factor essential to the control of cell proliferation, survival, differentiation, immune response, and inflammation. Constitutive NF-kappaB activation has been observed in a broad variety of solid tumors and hematological malignancies, which suggests that NF-kappaB signaling may perform a critical role in the development of human cancers. Interferon regulatory factor-2 (IRF-2), an antagonistic transcriptional repressor of IRF-1, evidences oncogenic potential, but little is currently known regarding the mechanism underlying the oncogenic activities of IRF-2. In this study, we report that IRF-2 recruits RelA/p65 transcription factors into the nucleus via physical interaction. While the nuclear recruitment of RelA by IRF-2 augments TNFalpha-induced NF-kappaB dependent transcription, the N-terminal truncated mutant form of IRF-2 inhibits the nuclear localization of RelA, and thus interferes with NF-kappaB activation. Furthermore, the knockdown of IRF-2 by IRF-2 siRNA attenuates TNFalpha-induced NF-kappaB dependent transcription by inhibiting the nuclear localization of RelA. Thus, these results show that IRF-2 regulates NF-kappaB activity via the modulation of NF-kappaB subcellular localization.
