title: Hydroxyurea inhibits the transactivation of the HIV-long-terminal repeat (LTR) promoter.
abstract: HIV-1 gene expression is regulated by the promoter/enhancer located within the U3 region of the proviral 5' LTR that contains multiple potential cis-acting regulatory sites. Here we describe that the inhibitor of the cellular ribonucleoside reductase, hydroxyurea (HU), inhibited phorbol myristate acetate- or tumour necrosis factor-alpha-induced HIV-1-LTR transactivation in both lymphoid and non-lymphoid cells in a dose-dependent manner within the first 6 h of treatment, with a 50% inhibitory concentration of 0.5 mM. This inhibition was found to be specific for the HIV-1-LTR since transactivation of either an AP-1-dependent promoter or the CD69 gene promoter was not affected by the presence of HU. Moreover, gel-shift assays in 5.1 cells showed that HU prevented the binding of the NF-kappaB to the kappaB sites located in the HIV-1-LTR region, but it did not affect the binding of both the AP-1 and the Sp-1 transcription factors. By Western blots and cell cycle analyses we detected that HU induced a rapid dephosphorylation of the pRB, the product of the retinoblastoma tumour suppressor gene, and the cell cycle arrest was evident after 24 h of treatment. Thus, HU inhibits HIV-1 promoter activity by a novel pathway that implies an inhibition of the NF-kappaB binding to the LTR promoter. The present study suggests that HU may be useful as a potential therapeutic approach for inhibition of HIV-1 replication through different pathways.
authors.affiliation: Departamento de Biología Celular, Fisiología e Inmunología, Facultad de Medicina, Universidad de Córdoba, Córdoba, Spain.
authors.forename: M A
authors.initials: MA
authors.lastname: Calzado
authors.forename: A
authors.initials: A
authors.lastname: MacHo
authors.forename: C
authors.initials: C
authors.lastname: Lucena
authors.forename: E
authors.initials: E
authors.lastname: Muñoz
mesh_terms: D015703:Antigens, CD / Q000235:genetics; D000945:Antigens, Differentiation, T-Lymphocyte / Q000235:genetics; D002453:Cell Cycle / Q000187:drug effects; D002461:Cell Line, Transformed; D005786:Gene Expression Regulation / Q000187:drug effects; D015967:Gene Expression Regulation, Viral / Q000187:drug effects*; D016322:HIV Enhancer / Q000187:drug effects*; D006367:HeLa Cells; D006801:Humans; D006918:Hydroxyurea / Q000494:pharmacology*; D019169:Jurkat Cells; D037181:Lectins, C-Type; D016328:NF-kappa B / Q000378:metabolism; D010766:Phosphorylation; D016160:Retinoblastoma Protein / Q000378:metabolism; D012264:Ribonucleotide Reductases / Q000037:antagonists & inhibitors*; D014158:Transcription, Genetic / Q000187:drug effects; D015533:Transcriptional Activation / Q000187:drug effects*; D000099192:CD69 Antigens
chemical_list: D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D006918:Hydroxyurea; D037181:Lectins, C-Type; D016328:NF-kappa B; D016160:Retinoblastoma Protein; D012264:Ribonucleotide Reductases; D000099192:CD69 Antigens