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Beschreibung

Histones play a central role in transcription regulation, DNA repair, DNA replication and chromosomal stability. Histone H3 is one of the five main histone proteins involved in the structure of chromatin in eukaryotic cells. It is a core component of nucleosome. Nucleosomes wrap and compact DNA into chromatin, limiting DNA accessibility to the cellular machineries which require DNA as a template. Featuring a main globular domain and a long N-terminal tail, H3 is involved with the structure of the nucleosomes of the 'beads on a string' structure. The N-terminal tail of histone H3 protrudes from the globular nucleosome core and can undergo several different types of epigenetic modifications that influence cellular processes. Both H3.X and H3.Y are two novel primate-specific Histone H3 variants that are not found other mammals or lower eukaryotes. H3.X and H3.Y mRNAs are expressed in transformed cell lines, such as U2OS, and in low amounts in human bone, breast and lung tissue. They exhibit amino acid sequence homology with other H3 variants, but differ in several functionally important residues, such as serine10 (S to A) and Serine 28 (S to R). Knockdown of H3.Y variant is shown to affect cell growth and leads to changes in the expression of many genes involved in cell cycle control. It is noteworthy that the number of cells expressing H3.Y is increased under stress stimuli.(Ref.: Wiedemann, SM et al. (2010). J. Cell Biol. 90(5), 777-791).