Fig. 1

The three replication-dependent histone gene clusters in mammals. Gene symbols are shown across the top; species and chromosomal location of each cluster is indicated at the side. Black = non-histone genes, pink = histone H1 genes, yellow = H2A genes, red = H2B genes, blue = H3 genes, green = H4 genes. Pseudogenes are indicated by a gray box around the gene (pseudogenes have the same symbol as their protein-coding orthologs but end with -ps for mouse and P for the other species). A paler shade indicates that the gene is present but currently unannotated and unnamed; a blank space indicates that the gene is missing entirely. Mouse H1 genes contain an ‘f’ in place of the hyphen, so each mouse H1f symbol is shown above each relevant mouse gene. A: The largest replication-dependent cluster, also known as HIST1. There are two large gaps in the cluster in all species. Conservation between species is remarkable, although there are some species-specific duplications, gene losses and in situ pseudogenizations. Mouse has an expansion at the end of the cluster—these genes are shown with the mouse gene symbol format; note that all mouse symbols follow this format but for simplicity only the uppercase format used for other mammalian genes is shown for the conserved genes. B. The second largest replication-dependent cluster, also known as HIST2; each species has at least 10 genes in this cluster that contains genes for the 4 core histones but contains no histone H1 genes. The cluster contains a large inverted repeat, indicated by brackets. C. The third mammalian replication-dependent cluster, also known as HIST3. Note that H3-4 has an exceptional symbol due to the common usage of the H3.4 symbol for the protein encoded by this gene, the systematic H3C16 alias is shown in parentheses