Histone H4: ProductsHistone 4 (H4/HIST1H4I; also H4M and HIST4H4) is a 12-15 kDa member of the histone H4 family of molecules. It is ubiquitously expressed, with H4 initially synthesized and deposited in replicating chromatin during S phase. H4 undergoes multiple posttranslational modifications. At the G2/M transition, H4 is monomethylated on Lys20 and possibly contributes to transcription initiation/elongation. As the cell moves into the M/G1 phase, Lys20 becomes either dimethylated or trimethylated, contributing to DNA repair and telomere maintenance, respectively. H4 is also known to be phosphorylated on Ser2 and 48, plus Tyr52 and 89, and acetylated on at least nine sites. Human histone 4 is 103 amino acids (aa) in length. Full length histone 4 is identical in aa sequence to mouse histone 4, and 78% aa identical to Tetrahymena histone 4 over aa 2-20 used for immunization.