Functional Analysis of KAP1 Requirements for HIV-1 Transcription and Latency Reactivation
HIV-1 latency maintenance and reactivation are regulated by several viral and host factors. One such regulator is Krüppel-associated box (KRAB)-associated protein 1 (KAP1: also named TRIM28 or TIF1β). While initial studies have revealed KAP1 to be a positive regulator of latency reversal in transformed and primary CD4+ T cells, subsequent studies have proposed KAP1 to be a repressor required for latency maintenance. Given this discrepancy, here we re-examine KAP1 transcription regulatory functions using a chemical genetics strategy to acutely deplete KAP1 expression to avoid the accumulation of indirect effects. KAP1 acute loss dampened HIV-1 promoter activity in response to activating signals, a function that can be restored upon complementation with exogenous KAP1, thus revealing KAP1-mediated activation is on target. By combining comprehensive KAP1 domain deletion and mutagenesis in a cell-based reporter assay, I genetically defined the RING finger domain and an Intrinsically Disordered Region as key activating features. However, KAP1 acute loss in a physiological relevant model, reveals limitations compared to chronic silencing of KAP1 in the same system. I also identified a potential co-factor MAGE-D2 from previous biochemical and genetic screens that interacts with KAP1. MAGE-D2 mimics KAP1s ability to activate HIV-1 latency reactivation in response to stimulation suggesting they form a complex to regulate the proviral genome. Together, this study solidifies the notion that KAP1 activates HIV-1 transcription by exploiting its multi-domain protein arrangement through previously unknown domains and functions. Also, this study highlights the need for better techniques to assess the direct consequence of KAP1 loss.
HIV-1, Transcriptional Activation, Tripartite Motif-Containing Protein 28
University of Texas Southwestern Medical Center
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