H3F3B

H3F3B is a human gene that encodes the histone variant H3.3B, one of two genes in humans that specify the replication-independent histone H3.3. Histone H3.3 variants are incorporated into chromatin outside of DNA replication and play important roles in regulating gene expression and chromatin structure.

The H3F3B gene is part of the H3F3 family, and its product H3.3B is a close homolog of H3.3A (encoded by H3F3A). Compared with canonical histone H3, H3.3 proteins carry specific amino acid differences that confer distinct properties. The H3.3 variants are highly conserved across vertebrates, reflecting their essential functions in chromatin biology.

Functionally, H3.3 is deposited into chromatin by specialized histone chaperones. The HIRA complex generally mediates replication-independent deposition at active chromatin regions, including promoters and gene bodies, while the ATRX–DAXX complex targets H3.3 to telomeres and pericentromeric heterochromatin. The presence of H3.3 in these regions is associated with transcriptional activity, chromatin accessibility, and the maintenance of epigenetic information during development and cellular stress.

Expression patterns for H3F3B are widespread across tissues, reflecting a general role in chromatin maintenance. In disease contexts, mutations in the related H3F3A gene are well documented in certain pediatric brain tumors, but disease associations specific to H3F3B are less clearly defined and are not as well characterized.

Evolutionarily, H3F3B is conserved among vertebrates, underscoring the fundamental role of H3.3 in chromatin dynamics and epigenetic regulation. It remains a focus in studies of chromatin remodeling, transcriptional control, and genome stability.