The chicken histone gene family.

1. Most of the chicken 43 core and H1 histone genes belong to two major histone gene clusters. 2. Each of six H1 genes encodes a different H1 protein sequence. 3. The known core histone genes, four H2A, seven H2B, and seven H3 genes, respectively, encode two, three and three different protein variants, whereas the four known H4 genes encode the same amino acid sequence. 4. The core histone genes have particular transcription regulatory elements within the 5'-flanking regions and the regulations of their expressions are distinct, even though they are members of the same core histone gene family. 5. There are some undefined differences in the DNA structures of the particular core histone genes in various chicken tissues and these structural variations probably result in differences in their transcriptional regulation.