Transcriptional Circuit Fragility Influences HIV Proviral Fate
Transcriptional circuit architectures can be evolutionarily selected to precisely dictate a given response. Unlike these cellular systems, HIV is regulated through a complex circuit composed of two successive phases (host and viral), which create a positive feedback loop facilitating viral replication. However, it has long remained unclear whether both phases operate identically and to what extent the host phase influences the entire circuit. Here we report that while the host phase is regulated by a checkpoint whereby KAP1 mediates transcription activation, the virus evolved a minimalist system bypassing KAP1. Given the complex circuits architecture, cell-to-cell KAP1 fluctuations impart heterogeneity in the host transcriptional responses thus affecting the feedback loop. Mathematical modeling of a complete circuit reveals how these oscillations ultimately influence homogeneous reactivation potential of a latent virus. Thus, while HIV drives molecular innovation to fuel robust gene activation, it experiences transcriptional fragility thereby influencing viral fate and cure efforts.\n\nIn BriefHIV evolved a minimalist but robust transcriptional circuit bypassing host regulatory checkpoints; however, the fragility of the circuit in the host phase (which primes HIV for activation) largely affects proviral transcription and fate.\n\nHighlightsO_LIThe host and viral phases of the HIV transcriptional circuit have different functional requirements\nC_LIO_LIHIV evolved a minimalist program to robustly bypass host cell regulatory checkpoints\nC_LIO_LIA mathematical model reveals that the host phase is subject to transcriptional circuit fragility\nC_LIO_LIHost transcriptional circuit fragility influences the viral feedback and latency reversal potential\nC_LI