H3 Histone Family 3A (H3F3A)

Histones are the basic nuclear proteins responsible for the nucleosome structure within the chromosomal fiber in eukaryotes. Five classes of histone genes have been reported. Some classes are expressed only during S phase, while others are replication independent. The latter are referred to as replacement histones and are expressed in quiescent or terminally differentiated cells. H3.3 is a replacement histone that is encoded by 2 distinct replication-independent genes, H3.3A (H3F3A) and H3.3B (H3F3B). The proteins encoded by the H3.3A and H3.3B genes are identical.Chalmers and Wells (1990) showed that the rabbit H3.3a 3-prime untranslated region is 94% similar to the human sequence of Wells and Kedes (1985), indicating that evolutionary conservation extends beyond the coding region.