PERMANENT OCCUPANCY OF THE HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 ENHANCER BY NF-KAPPA-B IS NEEDED FOR PERSISTENT VIRAL REPLICATION IN MONOCYTES

This work aimed to ascertain the role of kappa B-responsive elements o f the human immunodeficiency virus type 1 (HIV-1) enhancer not only in early initiation but also in long-term maintenance of proviral transc ription in cells of the monocytic lineage. For this purpose, we used t hree main approaches, The first was to abruptly terminate tumor necros is factor-induced NF-kappa B binding to the enhancer sequences in U1 m onocytic cells, using a short pulse of exogenous tumor necrosis factor . This resulted in concomitant decrease in nuclear NF-kappa B DNA-bind ing activity and endogenous long terminal repeat transcriptional activ ity, The second was to suppress the permanent NF-kappa B translocation induced by HIV-1 replication itself in chronically infected U937 cell s, using a specific proteasome inhibitor (Z-LLL-H). As early as 2 h af ter addition of the inhibitor to the culture medium, there was an inhi bition of both constitutive activation of NF-kappa B and HIV-1 genome expression. The third approach was to monitor the replication competen ce in U937 cells of an infectious HIV-1 provirus carrying point mutati ons in the kappa B-responsive elements of both long terminal repeats, Compared with its wild-type counterpart, this mutated provirus showed a profoundly decreased, Z-LLL-H-insensitive transcriptional and replic ative activity in U937 monocytes. Together, our results indicate that occupancy of the viral enhancer by KF-kappa B (p50/p65) heterodimers i s required for ongoing transcription of integrated HIV provirus in mon ocytes, even in cells chronically infected and permanently producing f unctional HIV Tat protein, Thus, the ability of HIV-1 replication to a ctivate NF-kappa B is crucial to the intense self-perpetuated viral tr anscription observed in cells of the monocytic lineage.