A SOLITARY HUMAN H3 HISTONE GENE ON CHROMOSOME-1

A solitary histone H3 gene encoding a novel H3 protein sequence has be en isolated. This H3 gene maps to chromosome 1 (1q42), whereas we have shown previously that the majority of the human histone genes form a large cluster on chromosome 6 (6p1.3). In addition, a small cluster ha s been described at 1q21. The clustered histone genes are expressed du ring the S-phase of the cell cycle, hence their definition as replicat ion-dependent histone genes. In contrast, expression of replacement hi stone genes is essentially cell-cycle independent; they are solitary g enes and map outside the major clusters. The newly described H3 gene m aps outside all known histone gene clusters and varies by four amino a cid residues from the consensus mammalian H3 structure. In contrast to other solitary histone genes, this human H3 gene shows the consensus promoter and 3' flanking portions that are typical for replication-dep endent genes.