CHARACTERIZATION OF THE MOUSE HISTONE GENE-CLUSTER ON CHROMOSOME-13 -45 HISTONE GENES IN 3 PATCHES SPREAD OVER 1 MB

The histone gene cluster on mouse chromosome 13 has been isolated and characterized. Using overlapping YAC clones containing histone genes f rom chromosome 13, a contig of similar to 2 Mb has been defined. It co ntains 45 histone genes, organized in three patches containing tightly clustered genes. An 80-kb patch (patch III) containing 12 histone gen es is near one end of the contig, and a similar-sized patch (patch I) containing IS histone genes is near the other end of the contig, locat ed at least 500 kb from the central patch (patch II) of histone genes. The entire cluster contains six histone H1 genes, including the testi s-specific histone Hlt gene that maps to the middle of the cluster. Al l nine histone H3 genes in this cluster have been sequenced, and their level of expression determined. Each histone H3 gene is distinct, wit h five genes encoding the H3.2 protein subtype and four genes encoding the H3.1 protein. They are all expressed, with each histone H3 gene a ccounting for a small proportion of the total histone H3 mRNA.