Each H2A/H2B gene pair is controlled by a divergent promoter spanning 300 to 330 nucleotides between the coding regions of the two genes.     ///    The highly conserved divergent H2A/H2B promoters can be classified in two groups based on the patterns of consensus sequence elements.     ///    "14 of these are organized as H2A/H2B gene pairs, while one H2A gene and three H2B genes are solitary genes. "