Multiple mechanisms are implicated in the regulation of NF-kappa B activity during human cytomegalovirus infection.
Infection-induced activation of the human cytomegalovirus major immediate early enhancer/promoter has been shown to be regulated primarily by transcription factor NF-kappa B cis elements. However, the mechanism(s) by which human cytomegalovirus induces NF-kappa B activity is unknown. A study was therefore undertaken to determine how this virus would affect normal NF-kappa B regulation. Viral infection of fibroblasts resulted in the specific stimulation of promoters containing major histocompatibility complex NF-kappa B cis elements fused upstream of the chloramphenicol acetyltransferase reporter gene. Electrophoretic mobility shift assays of nuclear extracts derived from mock- and virus-infected cells showed dramatic and sustained increases in DNA-binding proteins specific for these NF-kappa B sequences. Experiments using MAD-3 I kappa B, a specific inhibitor of NF-kappa B, and antibodies directed against rel family members demonstrated that the induced binding activities contained p50 and p65 proteins but not c-rel. Northern analysis indicated maximal levels of p50 mRNA by 4 h postinfection, whereas p65 and MAD-3 I kappa B mRNA accumulation peaked at 48-72 h postinfection, suggesting different regulatory mechanisms for p50 and p65/I kappa B genes. Electrophoretic mobility shift assays with deoxycholate-treated cytoplasmic extracts demonstrated a 3- to 4-fold decrease in the cytosolic stores of NF-kappa B binding activity by 4 h postinfection. Western blots probed with antibodies directed against MAD-3 I kappa B or pp40 (a protein isolated from chicken with sequence and biochemical properties similar to those of MAD-3 I kappa B) indicated that a cross-reactive peptide of 39 kDa was no longer detectable after 24 h postinfection. These results demonstrate that the activation and maintenance of nuclear NF-kappa B DNA binding and enhancer activities upon human cytomegalovirus infection occurs by multiple mechanisms.
Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina, Chapel Hill 27599-7295.
T F
TF
Kowalik
B
B
Wing
J S
JS
Haskill
J C
JC
Azizkhan
A S
AS
Baldwin
E S
ES
Huang
D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D003429:Cross Reactions; D003586:Cytomegalovirus Infections / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D005347:Fibroblasts; D006801:Humans; D020672:I-kappa B Proteins; D008969:Molecular Sequence Data; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D015533:Transcriptional Activation; D014764:Viral Proteins / Q000276:immunology
D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D012333:RNA, Messenger; D014764:Viral Proteins; C079504:pp40 protein, Human herpesvirus 5; D000072000:NF-KappaB Inhibitor alpha