Evidence for a human histone gene cluster containing H2B and H2A pseudogenes.

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Abstract
Not all members of the human histone gene family are functional. A human H2B pseudogene was isolated that contains alterations in the protein-coding sequences as well as in the 3'' and 5'' flanking sequences that preclude expression of a functional H2B histone protein. There are 3 modifications in the amino acid-coding region: a single-base deletion producing a frame shift, a single-base substitution resulting in a codon change from Ser to Try (an amino acid not present in histones), and the absence of a stop codon. Analysis of nucleotide sequences upstream from the AUG start signal indicates the absence of a TATA box and other putative consensus regulatory sequences. In the 3'' flanking region, a highly conserved block of 22 nucleotides that exhibits hyphenated dyad symmetry is displaced downstream. Within the same genomic segment, the adjacent H2A histone gene is missing 12 nucleotides, resulting in a deletion of 4 amino acids in a highly conserved region of the protein.