Two gamma interferon-activated site-like elements in the human cytomegalovirus major immediate-early promoter/enhancer are important for viral replication.
Human cytomegalovirus (HCMV) infection directly initiates a signal transduction pathway that leads to activation of a large number of cellular interferon-stimulated genes (ISGs). Our previous studies demonstrated that two interferon response elements, the interferon-stimulated response element and gamma interferon-activated site (GAS), in the ISG promoters serve as HCMV response sites (VRS). Interestingly, two GAS-like VRS elements (VRS1) were also present in the HCMV major immediate-early promoter-enhancer (MIEP/E). In this study, the importance of these VRS elements in viral replication was investigated. We demonstrate that the expression of the major IE genes, IE1 and IE2, is interferon inducible. To understand the biological significance of this signal transduction pathway in HCMV major IE expression, the two VRS1 in the MIEP/E were mutated. Mutant HCMVs in which the VRS elements were deleted or that contained point mutations grew dramatically more slowly than wild-type virus at a low multiplicity of infection (MOI). Insertion of wild-type VRS1 into the mutant viral genome rescued the slow growth phenotype. Furthermore, the expression levels of major IE RNAs and proteins were greatly reduced during infection with the VRS mutants at a low MOI. HCMV microarray analysis indicated that infection of host cells with the VRS mutant virus resulted in a global reduction in the expression of viral genes. Collectively, these data demonstrate that the two VRS elements in the MIEP/E are necessary for efficient viral gene expression and replication. This study suggests that although the HCMV-initiated signal transduction pathway results in induction of cellular antiviral genes, it also functions to stimulate viral major IE gene expression. This might be a new viral strategy in which the pathway is used to regulate gene expression and play a role in reactivation.
Netterwald
James
J
Department of Microbiology and Molecular Genetics, UMDNJ-New Jersey Medical School, 225 Warren St., Newark, NJ 07101-1709, USA.
Yang
Shaojun
S
Wang
Weijia
W
Ghanny
Salena
S
Cody
Michael
M
Soteropoulos
Patricia
P
Tian
Bin
B
Dunn
Walter
W
Liu
Fenyong
F
Zhu
Hua
H
D001483:Base Sequence; D003587:Cytomegalovirus / Q000235:genetics* / Q000276:immunology / Q000502:physiology; D017931:DNA Primers; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D017781:Genes, Immediate-Early / Q000235:genetics*; D006801:Humans; D007231:Infant, Newborn; D007371:Interferon-gamma / Q000276:immunology*; D008297:Male; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics*; D017384:Sequence Deletion; D012867:Skin / Q000276:immunology / Q000821:virology; D014779:Virus Replication / Q000235:genetics
D017931:DNA Primers; D007371:Interferon-gamma