Extracellular human immunodeficiency virus type 1 Tat protein is associated with an increase in both NF-κB binding and protein kinase C activity in primary human astrocytes

Human immunodeficiency virus type 1 (HIV-1) infection has been associated with an increase in the binding of the transcription factor NF-κB to its consensus sequence in the viral promoter. Using cultures of primary human fetal astrocytes, we show that exogenous HIV-1 Tat protein, which has been demonstrated to be released from infected cells, is associated with an increase in the binding of this transcription factor to an HIV-1 long terminal repeat κB sequence. This effect occurs rapidly and is independent of new protein synthesis. We also demonstrate that extracellular Tat protein is associated with an increase in protein kinase C activity. If Tat functions similarly in other cell types, such findings could relate to some of this protein's previously described physiological effects. These effects include Tat's ability to upregulate the synthesis of specific cytokines and to act as a growth factor.