Human Cytomegalovirus Immediate-Early 2Prote in Transactivates c-jun Promoter Through ATF and MEF2 Site / 감염

BACKGROUND: Human cytomegalovirus (HCMV) has the ability to activate the expression of many viral and cellular genes. The c-jun proto-oncogene has known to be induced at immediate early time of HCMV infection, however, the mechanism of up-regulation of the gene was not known. We found HCMV immediate-early (IE) 2 expression transactivate the c-jun promoter in human embryonal lung cell (HEL). METHODS: The c-jun promoter region between -117 and -59 contains binding sites for the transcription factors Sp1, CAAT, AP-1 like (ATF/CREB), and MEF2. We tried to map the sequences in the c-jun promoter responsible for activation of the promoter by HCMV IE2 expression. Transient expression assays were performed using various reporter plasmids containing the c-jun promoter-regulatory region linked to the luciferase gene and a plasmid expressing HCMV IE2 gene. RESULTS: Deletional and point mutational analysis showed that ATF, MEF2, and another down stream elements were involved in the up-regulation of c-jun promoter. Gel mobility shift assay showed that there are several factors in HEL cell nuclear extracts that specifically bind to these sites and in vitro translated IE2 could not move or supershift the specific bands. CONCLUSION: This study delineate the mechanism of c-jun up-regulation in HCMV infection and would give the clue for the possible contribution of HCMV in tumorigenesis.

The Change of c-jun Promoter Activity in TPA-Induced U937 Cells Infected with Human Cytomegalovirus (HCMV)

Transient transfection assay has been done to evaluate whether the c-jun activation would be prerequisite to the induction of permissiveness against human cytomegalovirus using in vitro cell model in which U937 has been induced to express CD11b and CDl4 to become potential monocyte/macrophage cells by TPA treatment. U937 cells were treated with 10 microM, 50 microM or 100 microM of TPA. The cell morphology change was observed and the expression of the CD11b and CDl4 was confirmed by FACS. Differentiated cells were transfected with pJLuc reporter vector which contained the wild type murine c-jun promoter spanning the SP1, CTF, ATF/CREB and MEF-2 binding sites upstream of the firefly luciferase gene. After 48 hrs of transfection, the cells were infected with HCMV Towne strain and the luciferase activity was assessed at 1 h and 4 h pi. The transfection assay showed no activation of the c-jun promoter at 1 h pi, instead, it showed 2 times increase of the its activity at 4 h pi. There was no difference of the c-jun promoter activation between TPA treated and untreated U937 cells, implying that c-jun activation might not be prerequisite for allowing cells to be premissive to HCMV, although HCMV infection itself could activate c-jun promoter.

The Change of c-jun Promoter Activity in TPA-Induced U937 Cells Infected with Human Cytomegalovirus (HCMV)

Transient transfection assay has been done to evaluate whether the c-jun activation would be prerequisite to the induction of permissiveness against human cytomegalovirus using in vitro cell model in which U937 has been induced to express CD11b and CDl4 to become potential monocyte/macrophage cells by TPA treatment. U937 cells were treated with 10 microM, 50 microM or 100 microM of TPA. The cell morphology change was observed and the expression of the CD11b and CDl4 was confirmed by FACS. Differentiated cells were transfected with pJLuc reporter vector which contained the wild type murine c-jun promoter spanning the SP1, CTF, ATF/CREB and MEF-2 binding sites upstream of the firefly luciferase gene. After 48 hrs of transfection, the cells were infected with HCMV Towne strain and the luciferase activity was assessed at 1 h and 4 h pi. The transfection assay showed no activation of the c-jun promoter at 1 h pi, instead, it showed 2 times increase of the its activity at 4 h pi. There was no difference of the c-jun promoter activation between TPA treated and untreated U937 cells, implying that c-jun activation might not be prerequisite for allowing cells to be premissive to HCMV, although HCMV infection itself could activate c-jun promoter.

Mapping of Human Cytomegalovirus IE1 Responsive Elements in the c-jun Promoter

Human cytomegalovirus (HCMV) has the ability to activate the espremission of many viral and cellular genes. Among various viral proteins, the immediate early proteins (IE1-72kDa, IE2-86kDa) have been known to be potent transactivators. The product of c-jun photo-oncogene is important in cell activation and differentiation. Here, we tried to find out if the IE could activate the c-jun promoter and also tried to identify the responsible sequence elements in the c-jun activation by IE1-72kDa. We found HCMV IE expression transactivated the c-jun promoter in human embryonal lung fibroblasts (HEL). The activation fold by IE1-72kDa, IE2-86kDa and IE2-55kBa was 23, 35, and 5, respectively. When the expression of each IE was combined, it showed synergism. Expression of (IE1-72kDa + IE2-86kBa) and (IE1-72kDa + IE2-86kDa + IE2-55kDa) resulted in 131 and 162 fold increase, respectively. The c-jun promoter region between -117 and -59 contains binding sites for the transcription factors Spl, CAAT, AP-1 like (ATF/CREB), and MEF2. Transient expression assays were performed using various reporter plasmids containing the c-jun promoter-regulatory region linked to the luciferase gene and a plasmic expressing HCMV IE1 gene. Deletional and point mutational analysis showed that the sequence between -225 to -160 and the CTF binding site were involved in the up-regulation of c-jun promoter.