Differential Regulation of the HIV-1 LTR by Specific NF-κB Subunits in HSV-1-Infected Cells

AbstractPrevious studies have shown that expression of HIV-1 provirus was enhanced in cells co-infected with the herpes virus and that HSV-1-mediated induction of the HIV-1 provirus expression involved both NF-κB-dependent and NF-κB-independent mechanisms. Nuclear NF-κB complexes could be detected approximately 8 hr after HSV-1 infection. Using NF-κB-specific antibodies in a mobility shift assay, we have found that HSV-1 increases binding of p50, p65, and c-relto the HIV-1 NF-κB probe in both Jurkat T cells and NIH/3T3 cells. HSV-1 infection also increases transiently the levels of p50 mRNA but an increase in the level of p65 mRNA was not detected. Furthermore, HSV-1 infection induces a rapid degradation of the IκBα protein. Transfection of HIV-1 LTR CAT into cell lines which overexpressed individual NF-κB proteins showed the highest constitutive expression of CAT activity in cells overexpressing p65. Infection with HSV-1 further enhanced the expression of HIV-1 LTR CAT in cell lines producing p52, p100, and c-rel.In contrast, HSV-1 did not significantly enhance the expression of HIV-1 LTR CAT in cell lines overexpressing p105 and IκBγ. In the transient expression assay the p65/c-rel heterodimer was the most effective inducer of the HIV-1 LTR expression. Thus it appears that p65 plays a limited role in the NF-κB-dependent activation of the HIV-1 LTR following HSV-1 infection and that the stimulation is mediated by the p50/p65 and p65/c-rel heterodimers. Thus the magnitude of HIV-1 provirus induction depends on the relative levels of NF-κB subunits present in the infected cells