H3 Histone Family 3B (H3F3B)

H3F3B contains introns and its mRNA is polyadenylated, unlike most histone genes. The protein encoded is a replication-independent member of the histone H3 family. The amino acid sequence of H3.3B is identical to that of H3.3A, as well as to the amino acid sequences of H3.3 homologs in other species, including Drosophila. However, the nucleotide sequences of H3.3A and H3.3B differ substantially, especially in the 5-prime and 3-prime UTRs.Northern blot analysis detected 1.8- and 1.4-kb mRNAs, which differ due to alternative use of polyadenylation signals, in RNA from testis and the HEK293 embryonal kidney tumor cell line.H3.3B spans approximately 2.5 kb. It has 4 exons, the first of which is noncoding, and exhibits features characteristic of a histone H3.3 gene.