4-Phenylbutyric acid activates an NF-κB-Egr-1 axis to control myoblast proliferation and ECM gene expression.

Myogenic progression is tightly controlled by epigenetic mechanisms. Here, we demonstrate that the histone deacetylase inhibitor 4-phenylbutyric acid (4-PBA) selectively promotes myoblast proliferation without inducing myotube differentiation. Mechanistically, 4-PBA increases histone H3 acetylation at lysines 18 and 27 through HDAC5 suppression, resulting in activation of NF-κB p65. HDAC5 overexpression attenuates 4-PBA-induced histone H3 acetylation, NF-κB/early growth response 1 (Egr-1) activation, and myoblast proliferation, supporting a causal role for HDAC5 suppression. Chromatin immunoprecipitation identifies Egr-1 as a direct transcriptional target of NF-κB p65. Transcriptomic analyses reveal that Egr-1 regulates extracellular matrix- and myogenesis-associated gene programs, including nonfibrillar collagen genes. Together, these findings define an epigenetic mechanism by which 4-PBA modulates myoblast proliferation through HDAC5-dependent histone acetylation and NF-κB p65-Egr-1-driven transcriptional programs, providing insight into how epigenetic therapeutics influence skeletal muscle cell behavior.