ABSTRACT
The multifunctional papillomavirus E2 protein serves important roles in transcriptional activation and genome maintenance and cooperates with the viral E1 helicase for the initiation of viral DNA replication. The bovine papillomavirus genome contains seventeen E2 binding sites, largely concentrated within the long control region, and a single E1 binding site at the origin of viral replication. Using chromatin immunoprecipitation (ChIP) followed by restriction enzyme digestion and PCR, we show that BPV E1 was present only in the region of an active origin of replication and that BPV E2 remained attached to definable segments of the viral genome at specific stages of the cell cycle.
Subject(s)
Bovine papillomavirus 1/genetics , Cell Cycle , DNA-Binding Proteins/metabolism , Genome, Viral , Viral Proteins/metabolism , Virus Replication , Animals , Binding Sites , Bovine papillomavirus 1/physiology , Cattle , Cell Line , Chromatin Immunoprecipitation , DNA Replication , DNA, Viral/biosynthesis , MiceABSTRACT
Both host and viral factors play an important role in the pathogenesis of human immunodeficiency virus (HIV)-associated bran injury. In this study, the authors examined the interactions between tumor necrosis factor (TNF)-alpha, CXCR4, the alpha chemokine receptor, and three HIV isolates, including the T-tropic viruses, HIV-1(MN) and HIV-1(IIIB), and the dual tropic virus, HIV-1(89.6). The authors show by flow cytometry that treatment of differentiated SK-N-MC cells with TNF-alpha induces a significant increase in the cell surface expression of CXCR4 in a time- and dose-dependent manner. The effect is partly regulated at the level of transcription. To assess the biological significance of this finding, we show that TNF-alpha potentiates the ability of the above mentioned HIV isolates to induce neuronal apoptosis and that the effect is significantly reduced by pretreating cells with monoclonal antibodies to either CXCR4 and TNF-alpha. Together these results suggest that TNF-alpha may render neuronal cells vulnerable to the apoptotic effects of HIV by increasing the cell surface expression of CXCR4 and thus identify another mechanism by which TNF-alpha contributes to the pathogenesis of HIV-associated brain injury.
