Independently evolving chicken histone H2B genes: identification of a ubiquitous H2B-specific 5′ element

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Abstract
The DNA sequence of two chicken histone H2B genes has been determined. Both genes code for the same H2B subtype. Except for conserved “promoter” elements, the sequences 5′ to the protein coding regions are completely divergent, indicating that the genes are distantly related and are not evolving in concert. This presents an ideal situation for sequence comparisons. We have discovered a 13 bp, H2B specific homology block, 5′ CTCATTTGCATAC 3′ located close to the “TATA box”. This motif is conserved in all H2B gene leader regions so far sequenced. One of the H2B genes is closely linked, in a divergent arrangement, to an H2A gene, and sequence data suggests that the linked genes share promoter elements.