Histone H3.3 (H3.3) (H3.3)

H3-3A encodes the histone variant H3.3, a fundamental protein involved in the structural organization of chromatin and the regulation of gene expression [1, 4]. Unlike canonical histones that are deposited during DNA replication, H3.3 is incorporated into nucleosomes throughout the cell cycle, particularly at transcriptionally active sites and telomeres [4, 11]. It serves as a key epigenetic mark, influencing DNA repair, chromosomal stability, and cellular differentiation [15, 16]. Somatic mutations in H3-3A, such as the K27M and G34R/V substitutions, are potent drivers of pediatric high-grade gliomas and are collectively known as "oncohistones" [10, 15]. These mutations lead to global dysregulation of histone post-translational modifications, notably the loss of H3K27 trimethylation, which promotes tumorigenesis [10, 14]. Therapeutic efforts are currently focused on small molecules like ONC201 and various epigenetic modifiers that aim to restore normal chromatin states or exploit the unique vulnerabilities of mutant cells [6, 17, 19]. Beyond oncology, germline mutations in H3-3A are associated with Bryant-Li-Bhoj neurodevelopmental syndrome, highlighting its critical role in normal brain development [4, 13].

Other names

H3F3AH3.3AH3F3H3 histone family member 3AH3.3 histone ABRYLIB1

Epigenetic modulation, including inhibition of histone-modifying enzymes (EZH1/2, HDACs) and activation of mitochondrial proteases (ClpP) to counteract the effects of oncohistone mutations [6, 10, 17, 19].