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Human cytomegalovirus immediate early proteins upregulate endothelial p53 function
J Wang1, P H Marker, J D Belcher
1Cardiovascular Genetics Laboratory, University of New South Wales, Kensington, NSW, Australia.
Abstract:
Infected endothelial cells are found to be resistant to apoptosis possibly mediated by p53 cytoplasmic sequestration. We explored whether the immediate early 84 kDa protein (IE84) of cytomegalovirus (CMV) is responsible for p53 cytoplasmic sequestration. The endothelial cells were transfected with plasmids containing IE1 and 2 coding regions which are known to synthesize IE84 and 72 proteins. Our study found that p53 expression was significantly elevated in endothelial cells transfected with IE1 and 2 plasmids. However, p53 was only found in the nucleus rather than sequestered in the cytoplasm. We have demonstrated that IE84 and 72 are not responsible for p53 dysfunction caused by CMV infection, rather they upregulate p53 function and promote endothelial apoptosis.
Insights
Cytomegalovirus (CMV) infection in endothelial cells does not cause p53 dysfunction. Instead, CMV proteins IE84 and 72 enhance p53 activity, promoting cell death and increasing apoptosis resistance.
Area of Science:
- Cell Biology
- Virology
- Molecular Biology
Background:
- Endothelial cells infected with cytomegalovirus (CMV) exhibit resistance to apoptosis.
- This resistance is potentially linked to the sequestration of the p53 protein in the cytoplasm.
- The immediate early 84 kDa protein (IE84) of CMV is investigated as a potential mediator of this p53 sequestration.
Purpose of the Study:
- To investigate whether the CMV immediate early 84 kDa protein (IE84) is responsible for the cytoplasmic sequestration of p53 in infected endothelial cells.
- To determine the role of IE84 and IE72 proteins in p53 localization and function during CMV infection.
Main Methods:
- Transfection of endothelial cells with plasmids encoding the IE1 and IE2 coding regions of CMV, which synthesize IE84 and IE72 proteins.
- Analysis of p53 expression levels and subcellular localization (nucleus vs. cytoplasm) in transfected cells.
Main Results:
- p53 expression was significantly elevated in endothelial cells transfected with CMV IE1 and IE2 plasmids.
- Contrary to the hypothesis, p53 was predominantly found in the nucleus, not sequestered in the cytoplasm.
- The study demonstrated that IE84 and IE72 do not cause p53 dysfunction.
Conclusions:
- CMV IE84 and IE72 proteins are not responsible for p53 cytoplasmic sequestration or dysfunction.
- These viral proteins actually upregulate p53 function.
- The findings suggest that CMV IE84 and IE72 promote endothelial apoptosis, challenging the initial hypothesis of apoptosis resistance mediated by p53 sequestration.