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HIV-1 viral production is restricted intracellularly in astrocytes compared with lymphocytes due to the limited expression of viral structural proteins. The poor translation of HIV-1 mRNA and consequent limited virion production can be restored by overexpression of TRBP proteins in the astrocytoma U251MG cells. TRBP1 and TRBP2 are double-stranded RNA binding proteins that increase HIV-1 gene expression. Both proteins are produced from a single gene that possesses two independent promoters and an alternative first exon. Endogenous expression is restricted in astrocytes due to limited TRBP promoter expression compared to lymphocytes. We examined the transcriptional regulation of TRBP1 and TRBP2 by in vivo genomic footprinting in the lymphocytic Jurkat and in the astrocytic U251MG cells. We identified one AP4 and one AP2-binding site that regulate the TRBP2 promoter in both cell types, and one Sp1 and two CCAAT-binding sites that control TRBP1 expression. Mutations in the TRBP1 promoter modulate its expression specifically in Jurkat and in U251MG. The analysis of the CCAAT-390 site by EMSA and by ChIP demonstrates that NF-Y/CBF transcription factor binds specifically to the promoter in vitro and in vivo. Furthermore, each NF-Y subunit was more highly expressed in the lymphocytic cells, compared to astrocytic cells. An NF-YA trans-dominant mutant decreased TRBP1 promoter expression fourfold in Jurkat cells, thus demonstrating the functional importance of NF-Y factors in lymphocytes. These studies suggest that the cell specifity of HIV-1 expression and replication may be regulated, in part, through the control of TRBP1 expression. [Copyright &y& Elsevier]

The innate antiviral response mainly relies on the production of type I interferons (IFN α / β ) . IFNs establish a robust antiviral state through the induction of hundreds of interferon-stimulated genes (ISGs), which restrict virus replication and spreading. The inability of the host to sustain an antiviral response leads to failure in eradicating the infection. Conversely, uncontrolled duration of the antiviral response is associated with the development of autoimmune disorders. To reach the ideal duration for efficient fighting of the infection without generation of side effects, the antiviral response needs to be strictly regulated. However, these mechanisms are still barely characterized. We are studying the duration of the antiviral response against Paramyxoviruses in human airway epithelial cells. We performed a thorough analysis of the temporal involvement RIG-I and MDA5 in the regulation of IRF-3, a key regulator of the IFNB gene. Based on specific RNAi-mediated knockdown of RIG-I or MDA5, we unveiled that while RIG-I is critical for the initiation of IRF-3 activation, MDA5 rather prevents active IRF-3 degradation, thereby sustaining IRF-3 activation and downstream gene expression. Conversely, ectopic expression of MDA5 prolonged RIG-I-induced IRF-3 activation. Once IFNs are produced, they promote the expression of ISGs. The proinflammatory cytokine TNF α is secreted concomitantly to IFN β and was shown to act synergistically to trigger a delayed specific antiviral transcriptional program. We identified the DUOX2 and DUOXA2 genes amongst the late genes specifically induced by IFN β /TNF α . These genes encode for the H 2 O 2 -producing DUOX2 enzyme and its activator DUOXA2. Using a RNAi approach, we found that DUOX2-mediated extracellular H 2 O 2 release in human airway epithelial cells is required to sustain the level of IFN β and IFN λ at late time of infection. Altogether, our results identified two novel mechanisms that contribute to the duration of the IFN-mediated antiviral response in response to Paramyxoviruses. [ABSTRACT FROM AUTHOR]