Impact of HIV-1 Tat on FDFT1 Suppression, Changes in Cholesterol Level, and KSHV Replication in BCBL1 Cells.

Introduction: The present study investigated the molecular mechanism by which the transactivator of transcription (Tat) protein of Human Immunodeficiency Virus 1 (HIV-1) activates the replication cycle of Kaposi's Sarcoma-associated Herpesvirus (KSHV).

Methods: BCBL-1 cells were initially infected with lentivirus overexpressing HIV-1 Tat. The relative mRNA expression of Farnesyl Diphosphate Farnesyltransferase 1 (FDFT1), HIV-1 Tat, KSHV Open Reading Frame 73 (ORF73), and KSHV Open Reading Frame 50 (ORF50) was quantified by real-time fluorescent quantitative Polymerase Chain Reaction (RT-qPCR). The cellular cholesterol levels were determined using a total cholesterol assay kit. BCBL-1 cells treated with 12-O-tetradecanoylphorbol-13-acetate (TPA) served as a positive control for the lytic replication of KSHV. The relative mRNA expression levels of HIV-1 Tat, FDFT1, KSHV ORF73, and KSHV ORF50 were subsequently evaluated in BCBL-1 cells following infection with lenti-viruses for FDFT1 overexpression or FDFT1-RNAi knockdown, and the cellular cholesterol content was quantified.

Results: The findings revealed that HIV-1 Tat downregulated FDFT1 and upregulated the expression of KSHV ORF50 in BCBL-1 cells. FDFT1 overexpression upregulated the expression of the latency-associated gene, ORF73, of KSHV in BCBL-1 cells, while knockdown of FDFT1 upregulated the expression of genes associated with the lytic reactivation of KSHV. Infection with the HIV-1 lentivirus, which overexpresses Tat, as well as manipulation of FDFT1, significantly altered the cholesterol content in BCBL-1 cells.

Conclusion: The downregulation of FDFT1 by HIV-1 Tat modulates cellular cholesterol levels and is associated with KSHV replication in BCBL-1 cells.