The human immunodeficiency virus tat protein increases the transcription of human Alu repeated sequences by increasing the activity of the cellular transcription factor TFIIIC.

The HIV Tat protein is able to upregulate the transcription by RNA polymerase III of cotransfected or endogenous cellular Alu-repeated sequences in both HeLa and Jurkat T cells. This effect is mediated by an increase in the activity of transcription factor TFIIIC, which binds to the B box in the RNA polymerase III Alu promoter. This is the first example of an effect of the Tat protein on the transcription of a cellular gene or on the activity of a cellular transcription factor. The significance of this effect for the life cycle of HIV and its interaction with infected cells is discussed.