Histone H2A-Bbd type 3 (H2A.B.3)

Histone H2A-Bbd type 3 (H2A.B.3) is an atypical, replication-independent variant of the H2A family of core histones, characterized by significant sequence divergence from canonical H2A and a lack of the canonical C-terminal tail[1][2]. H2A.B.3 is incorporated into nucleosomes predominantly at actively transcribed genes, conferring a more relaxed and dynamic chromatin structure with altered DNA protection and increased DNA flexibility compared to canonical nucleosomes[1][3]. It plays important roles in transcriptional activation, including enhancing RNA polymerase II activity and facilitating pre-mRNA splicing by directly recruiting spliceosomal components through its N-terminal domain[2][3][5][6]. H2A.B.3 is associated with the regulation of ribosomal biogenesis and is essential for optimal cell proliferation, particularly in certain cancers[5]. Its incorporation destabilizes nucleosome-DNA interactions, potentially lowering the barrier for RNA polymerase passage, and may alter the "histone code" by lacking many canonical post-translational modification sites[1][7]. No therapeutic drugs or direct modulators of H2A.B.3 are reported in current databases, and it is not presently considered a classical therapeutic target such as a receptor, enzyme, or transporter[2][5][7].

Other names

H2AB3H2A.BbdH2A.Bbd type 2/3H2A-BbdH2AB2H2AFB2H2AFB3H2ABBDH2A.B.1H2A Barr body-deficientH2A histone family member B3H2A, Barr-body deficienthistone variant H2A, Barr-body deficient