Binding STAT2 by the acidic domain of human cytomegalovirus IE1 promotes viral growth and is negatively regulated by SUMO.
The human cytomegalovirus (HCMV) 72-kDa immediate-early 1 (IE1) protein is thought to modulate cellular antiviral functions impacting on promyelocytic leukemia (PML) nuclear bodies and signal transducer and activator of transcription (STAT) signaling. IE1 consists of four distinct regions: an amino-terminal region required for nuclear localization, a large central hydrophobic region responsible for PML targeting and transactivation activity, an acidic domain, and a carboxyl-terminal chromatin tethering domain. We found that the acidic domain of IE1 is required for binding to STAT2. A mutant HCMV encoding IE1(Delta421-475) with the acidic domain deleted was generated. In mutant virus-infected cells, IE1(Delta421-475) failed to bind to STAT2. The growth of mutant virus was only slightly delayed at a high multiplicity of infection (MOI) but was severely impaired at a low MOI with low-level accumulation of viral proteins. When cells were pretreated with beta interferon, the mutant virus showed an additional 1,000-fold reduction in viral growth, even at a high MOI, compared to the wild type. The inhibition of STAT2 loading on the target promoter upon infection was markedly reduced with mutant virus. Furthermore, sumoylation of IE1 at this acidic domain was found to abolish the activity of IE1 to bind to STAT2 and repress the interferon-stimulated genes. Our results provide genetic evidence that IE1 binding to STAT2 requires the 55-amino-acid acidic domain and promotes viral growth by interfering with interferon signaling and demonstrate that this viral activity is negatively regulated by a cellular sumoylation pathway.
Huh
Yong Ho
YH
Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, Gyeonggido, Republic of Korea.
Kim
Young Eui
YE
Kim
Eui Tae
ET
Park
Jung Jin
JJ
Song
Moon Jung
MJ
Zhu
Hua
H
Hayward
Gary S
GS
Ahn
Jin-Hyun
JH
D002460:Cell Line; D002478:Cells, Cultured; D003587:Cytomegalovirus / Q000254:growth & development*; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism*; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D025941:Protein Interaction Mapping; D050795:STAT2 Transcription Factor / Q000378:metabolism*; D025842:SUMO-1 Protein / Q000378:metabolism*; D017384:Sequence Deletion
C088645:IE1 protein, cytomegalovirus; D017874:Immediate-Early Proteins; D050795:STAT2 Transcription Factor; C494084:STAT2 protein, human; D025842:SUMO-1 Protein