RESUMO
EVER1 and EVER2 are mutated in epidermodysplasia verruciformis patients, who are susceptible to human betapapillomavirus (HPV) infection. It is unknown whether their products control the infection of other viruses. Here, we show that the expression of both genes in B cells is activated immediately after Epstein-Barr virus (EBV) infection, whereas at later stages, it is strongly repressed via activation of the NF-κB signaling pathway by latent membrane protein 1 (LMP1). Ectopic expression of EVER1 impairs the ability of EBV to infect B cells.
Assuntos
Epidermodisplasia Verruciforme/patologia , Regulação da Expressão Gênica , Herpesvirus Humano 4/fisiologia , Interações Hospedeiro-Patógeno , Proteínas de Membrana/biossíntese , Proteínas da Matriz Viral/metabolismo , Linfócitos B/virologia , Humanos , Proteínas de Membrana/genéticaRESUMO
Hypoxia Inducible Factor-1 (HIF-1) is essential for mammalian development and is the principal transcription factor activated by low oxygen tensions. HIF-α subunit quantities and their associated activity are regulated in a post-translational manner, through the concerted action of a class of enzymes called Prolyl Hydroxylases (PHDs) and Factor Inhibiting HIF (FIH) respectively. However, alternative modes of HIF-α regulation such as translation or transcription are under-investigated, and their importance has not been firmly established. Here, we demonstrate that NF-κB regulates the HIF pathway in a significant and evolutionary conserved manner. We demonstrate that NF-κB directly regulates HIF-1ß mRNA and protein. In addition, we found that NF-κB-mediated changes in HIF-1ß result in modulation of HIF-2α protein. HIF-1ß overexpression can rescue HIF-2α protein levels following NF-κB depletion. Significantly, NF-κB regulates HIF-1ß (tango) and HIF-α (sima) levels and activity (Hph/fatiga, ImpL3/ldha) in Drosophila, both in normoxia and hypoxia, indicating an evolutionary conserved mode of regulation. These results reveal a novel mechanism of HIF regulation, with impact in the development of novel therapeutic strategies for HIF-related pathologies including ageing, ischemia, and cancer.
Assuntos
Translocador Nuclear Receptor Aril Hidrocarboneto/genética , Regulação da Expressão Gênica , NF-kappa B/metabolismo , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Fibroblastos/efeitos dos fármacos , Redes Reguladoras de Genes/genética , Células HEK293 , Células HeLa , Humanos , Hipóxia/genética , Camundongos , NF-kappa B/genética , RNA Interferente Pequeno/genética , Transdução de Sinais , Fator de Necrose Tumoral alfa/farmacologiaRESUMO
HIF (hypoxia-inducible factor) is the main transcription factor activated by low oxygen tensions. HIF-1alpha (and other alpha subunits) is tightly controlled mostly at the protein level, through the concerted action of a class of enzymes called PHDs (prolyl hydroxylases) 1, 2 and 3. Most of the knowledge of HIF derives from studies following hypoxic stress; however, HIF-1alpha stabilization is also found in non-hypoxic conditions through an unknown mechanism. In the present study, we demonstrate that NF-kappaB (nuclear factor kappaB) is a direct modulator of HIF-1alpha expression. The HIF-1alpha promoter is responsive to selective NF-kappaB subunits. siRNA (small interfering RNA) studies for individual NF-kappaB members revealed differential effects on HIF-1alpha mRNA levels, indicating that NF-kappaB can regulate basal HIF-1alpha expression. Finally, when endogenous NF-kappaB is induced by TNFalpha (tumour necrosis factor alpha) treatment, HIF-1alpha levels also change in an NF-kappaB-dependent manner. In conclusion, we find that NF-kappaB can regulate basal TNFalpha and, in certain circumstances, the hypoxia-induced HIF-1alpha.
Assuntos
Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , NF-kappa B/metabolismo , Linhagem Celular Tumoral , Células Cultivadas , Humanos , Subunidade alfa do Fator 1 Induzível por Hipóxia/genética , RNA Mensageiro/metabolismo , RNA Interferente Pequeno/metabolismo , Transdução de SinaisRESUMO
Hypoxia induces a variety of cellular responses such as cell cycle arrest, apoptosis, and autophagy. Most of these responses are mediated by the hypoxia-inducible factor-1alpha. To induce target genes, hypoxia-inducible factor-1alpha requires a chromatin environment conducive to allow binding to specific sequences. Here, we have studied the role of the chromatin-remodeling complex SWI/SNF in the cellular response to hypoxia. We find that SWI/SNF is required for several of the cellular responses induced by hypoxia. Surprisingly, hypoxia-inducible factor-1alpha is a direct target of the SWI/SNF chromatin-remodeling complex. SWI/SNF components are found associated with the hypoxia-inducible factor-1alpha promoter and modulation of SWI/SNF levels results in pronounced changes in hypoxia-inducible factor-1alpha expression and its ability to transactivate target genes. Furthermore, impairment of SWI/SNF function renders cells resistant to hypoxia-induced cell cycle arrest. These results reveal a previously uncharacterized dependence of hypoxia signaling on the SWI/SNF complex and demonstrate a new level of control over the hypoxia-inducible factor-1alpha system.