Background: Changes in chromatin structure play a large role in the regulation of transcription in eukaryotes (1). The nucleosome is the primary building block of chromatin, and is made up of four core histone proteins (H2A, H2B, H3 and H4) (2). Acetylation of core histones regulates gene expression (2). Histone H3 is primarily acetylated at lysines 9, 14, 18, and 23 (3,4). Acetylation at lysine 9 appears to have a dominant role in histone deposition and chromatin assembly in some organisms (3,4). . H3t (H.34) differs from the consensus mammalian H3 structure by four amino acid residues and it is mainly expressed in testicular cells. H3t encoding gene maps to chromosome 1 (1q42), unlike the majority of the human histone genes that form cluster on chromosome 6 and outside of replication-dependent H3 genes (5).