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

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).

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.

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.

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