4-Phenylbutyric Acid Activates an NF-?B - Egr-1 Axis to Control Myoblast Proliferation and ECM Gene Expression Profiles

Myoblasts are proliferative precursors derived from satellite cells and play critical roles in skeletal muscle growth, regeneration, and repair. The transition from myoblast proliferation to differentiation is tightly controlled by epigenetic mechanisms, particularly histone acetylation. During myogenesis, increased histone acetylation at muscle-specific gene loci promotes chromatin accessibility and activates myogenic transcription programs. 4-Phenylbutyric acid (4-PBA) is a clinically approved drug that functions as a chemical chaperone and a histone deacetylase (HDAC) inhibitor. Although 4-PBA has been shown to improve protein homeostasis in muscle-related disorders, its epigenetic role in myogenesis remains unclear. In this study, we demonstrated that 4-PBA regulates myoblast proliferation but not differentiation through epigenetic and transcriptional mechanisms in C2C12 cells. Chromatin immunoprecipitation assays revealed early growth response-1 (Egr-1) as a direct transcriptional target of NF-?B p65. 4-PBA increases histone H3 acetylation, particularly at lysines 18 and 27, and downregulates HDAC5, inducing NF-?B p65–dependent Egr-1 expression. Transcriptome analysis revealed that Egr-1 regulates extracellular matrix and myogenesis-related genes, including multiple collagen genes. Similar gene expression changes were observed following 4-PBA treatment, suggesting that 4-PBA promotes extracellular matrix gene expression in part through modulation of the NF-?B–Egr-1 axis. These findings highlight a previously unrecognized epigenetic function of 4-PBA in skeletal myogenesis. Overall design: RNA-seq profiling of C2C12 cells treated with 1mM 4-Phenylbutyric Acid (PBA) or DMSO at Day0 (Baseline) and Day4 of myoblast differentiation.