Histone decrotonylation plays a distinct role in HIV latency.

The role of epigenetic regulation in HIV latency remains incompletely understood. We show that histone deacetylase 3 (HDAC3) inhibits trans-activator of transcription (Tat)-mediated HIV transcription through histone decrotonylation (HDCR), independent of deacetylase activity. Chemical biology approaches identified selective HDCR inhibitors (HDCRis) that reverse HIV latency with minimal impact on other histone acylations. Although HDAC2, HDAC3, and HDAC8 exhibit HDCR activity, genetic and chemical studies reveal that the HDCRi citarinostat is selective for HDAC3 and HDAC8. Molecular docking suggests that HDCRi binds outside the zinc-binding pocket, distinct from the classical HDAC inhibitor vorinostat (SAHA, suberoylanilide hydroxamic acid). Key residues (arginine-265, arginine-301, glutamine-113, and aspartic acid-57) are essential for HDCR selectivity, as their mutation abolishes HDCR activity and increases histone crotonylation without altering other acylation marks. Citarinostat increases histone crotonylation at the HIV long terminal repeat, robustly activating HIV transcription in cell lines, primary CD4