title: The activator protein 1 binding motifs within the human cytomegalovirus major immediate-early enhancer are functionally redundant and act in a cooperative manner with the NF-{kappa}B sites during acute infection.
abstract: Human cytomegalovirus (HCMV) infection causes a rapid induction of c-Fos and c-Jun, the major subunits of activator protein 1 (AP-1), which in turn have been postulated to activate the viral immediate-early (IE) genes. Accordingly, the major IE promoter (MIEP) enhancer, a critical control region for initiating lytic HCMV infection and reactivation from the latent state, contains one well-characterized AP-1 site and a second candidate interaction site. In this study we explored the role of these AP-1 elements in the context of the infection. We first show that the distal candidate AP-1 motif binds c-Fos/c-Jun heterodimers (AP-1 complex) and confers c-Fos/c-Jun-mediated activity to a core promoter. Site-directed mutagenesis studies indicate that both AP-1 response elements are critical for 12-O-tetradecanoylphorbol-13-acetate (TPA)-enhanced MIEP activity in transient-transfection assays. In marked contrast to the results obtained with the isolated promoter, disruption of the AP-1 recognition sites of the MIEP in the context of the infectious HCMV genome has no significant influence on the expression of the MIE protein IE1 or viral replication in different cell types. Moreover, a chimeric murine CMV driven by the HCMV MIEP (hMCMV-ES) with the two AP-1 binding sites mutated is not compromised in virulence, is able to grow and disseminate to different organs of the newborn mice as efficiently as the parental virus, and is competent in reactivation. We show, however, that combined inactivation of the enhancer AP-1 and NF-κB recognition sites leads to an attenuation of the hMCMV-ES in the neonatal murine infection model, not observed when each single element is abolished. Altogether, these results underline the functional redundancy of the MIEP elements, highlighting the plasticity of this region, which probably evolved to ensure maximal transcriptional performance across many diverse environments.
authors.affiliation: Institut d'Investigacions Biomèdiques August Pi i Sunyer, 08036 Barcelona, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Isern
authors.forename: Montse
authors.initials: M
authors.lastname: Gustems
authors.forename: Martin
authors.initials: M
authors.lastname: Messerle
authors.forename: Eva
authors.initials: E
authors.lastname: Borst
authors.forename: Peter
authors.initials: P
authors.lastname: Ghazal
authors.forename: Ana
authors.initials: A
authors.lastname: Angulo
mesh_terms: D000208:Acute Disease; D020816:Amino Acid Motifs / Q000235:genetics; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D045744:Cell Line, Tumor; D003587:Cytomegalovirus / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D003586:Cytomegalovirus Infections / Q000821:virology*; D004195:Disease Models, Animal; D004742:Enhancer Elements, Genetic; D017781:Genes, Immediate-Early; D006801:Humans; D017874:Immediate-Early Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D018146:Muromegalovirus / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D016328:NF-kappa B / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D020218:Response Elements; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014779:Virus Replication
chemical_list: D017874:Immediate-Early Proteins; D016328:NF-kappa B; D018808:Transcription Factor AP-1