Fig. 5

HBO1 promotes immune-related gene expression via histone acetylation. BRPF2 and HBO1 form complexes that bind to the enhancer and promoter of the CD8 gene, respectively. Together, they acetylate histone H3 at lysine 14 (H3K14ac) at the CD8 locus, leading to full activation of the CD8 gene. The BRPF2–HBO1 complex also interacts directly with key regulatory factors, such as the RUNX family transcription factors and Ikaros, to activate CD8 gene expression. SCML4, a transcription factor crucial for CD8+ resident memory T cells (Trm) and tumor-infiltrating lymphocytes (TIL), recruits the HBO1–BRPF2–ING4 complex to mediate H3K14ac, thereby enhancing chromatin accessibility during T cell activation and increasing the expression of T cell effector molecules, such as interferon-gamma (IFNG) and granzyme B (GZMB)