NF-κB cis-Acting Motifs of the Human Immunodeficiency Virus (HIV) Long Terminal Repeat Regulate HIV Transcription in Human Macrophages

The role of NF-κB in the reactivation of human immunodeficiency virus (HIV) from latency in CD4 T lymphocytes is well documented. However, its role in driving HIV transcription in human macrophages, which contain a constitutive nuclear pool of NF-κB, is less well understood. In this study we have investigated the role that the constitutive pool of NF-κB and the NF-κB cis-acting motifs of the HIV long terminal repeat (LTR) play in regulating HIV transcription in human monocytic cells and primary macrophages. Inhibition of the constitutive nuclear pool of NF-κB (RelA and RelB) in the promonocytic U937 cell line using dominant-negative IκBα significantly decreases HIV replication. Moreover, it is demonstrated that in the differentiated monocytic cell line THP1, which contains a constitutive nuclear pool of NF-κB (RelB),an HIV provirus containing mutations of the κB cis-acting sites in the LTR is transcriptionally impaired. Reduction of the constitutive pool of NF-κB in human macrophages by an adenovirus vector expressing a dominant-negative IκBα also reduces HIV transcription. Lastly, mutation of the NF-κB cis-acting sites in the LTR of an R5 HIV provirus completely abrogates the first cycle of HIV transcription. These studies indicate that the cis-acting NF-κB motifs of the HIV LTR are critical in initiating HIV transcription in human macrophages and suggest that the constitutive nuclear pool of NF-κB is important in regulating HIV transcription in these cells.