HDAC2 inhibition restores H4K16ac and delays senescence in HGPS VSMCs

Histone H4 lysine 16 acetylation (H4K16ac) controls chromatin compaction, replication-coupled chromatin maturation and double-strand break repair. It is also depleted in Hutchinson-Gilford progeria syndrome (HGPS) vascular smooth muscle cells (VSMCs). To identify the enzymes that set steady-state H4K16ac, we depleted KAT5, KAT8, all eleven zinc-dependent HDACs and all seven sirtuins in HeLa and U2OS cells, then in unaffected control and HGPS VSMCs. KAT8 depletion markedly reduced H4K16ac; KAT5 depletion had little effect. Among erasers, HDAC2 was dominant: its depletion or overexpression bidirectionally modulated H4K16ac, HDAC1 did neither, and SIRT1 depletion raised H4K16ac in these lines but far less in HGPS VSMCs. HDAC2-directed inhibitors (BRD4884, MI192, Santacruzamate A) restored H4K16ac in HGPS VSMCs, whereas the SIRT1 inhibitor EX527 did not. They also improved nuclear architecture, reduced {gamma}H2AX signaling, preserved Ki67 positivity across serial passage, and limited senescence-associated {beta}-galactosidase accumulation. HDAC2 is therefore the predominant class I regulator of steady-state H4K16ac and a candidate target for limiting senescence in HGPS VSMCs.