nucleosome

Repeating motif consisting of 146-147 base pairs of DNA wrapped around a histone octomer in left handed superhelix. The histone octomer of nucleosomes contains 2 molecules each of H2A, H2B, H3 & H4 assembled in one H3-H4 heterotetramer & 2 H2A-H2B heterodimers. Nucleosomes wrap & compact DNA into chromatin, limiting DNA accessibility to the cellular machineries which require DNA as a template. Nucleosomes can be in open or closed formation affecting accessibility to sequence specific transcription factors & DNA dependent enzymes such as RNA & DNA polymerases. Histones & nucleosomes thereby play a central role in transcription regulation, DNA repair, DNA replication & chromosomal stability. DNA accessibility is regulated via a complex set of post-translational modifications of histones, also called histone code, & nucleosome remodelling.

General

DNA motif molecular complex

Properties

SIZE: entity length = 140 KB COMPARTMENT: cell nucleus SUBUNITS: histone-H2A (2) MOTIF: binding site FOR-BINDING-OF: ubiquitin histone-H2B (2) MOTIF: calmodulin binding site FOR-BINDING-OF: calmodulin histone-H3 (2) histone H4 (2) MOTIF: acetylation site SITE: N-TERMINUS EFFECTOR-BOUND: acetyl Ser phosphorylation site {S2} DNA-binding motif SITE: 17-21 Ser phosphorylation site {S48} Tyr phosphorylation site {Y52} Tyr phosphorylation site {Y89} deoxyribonucleic acid (DNA)

References

Kim et al. Immunity 10:345-355, 1999

Components

deoxyribonucleic acid (DNA) histone H4 (HIST1H4A, H4/A, H4FA, HIST1H4B, H4/I, H4FI, HIST1H4C, H4/G, H4FG, HIST1H4D, H4/B, H4FB, HIST1H4E, H4/J, H4FJ, HIST1H4F, H4/C, H4FC, HIST1H4H, H4/H, H4FH, HIST1H4I, H4/M, H4FM, HIST1H4J, H4/E, H4FE, HIST1H4K, H4/D, H4FD, HIST1H4L, H4/K, H4FK, HIST2H4A, H4/N, H4F2, H4FN, HIST2H4, HIST2H4B, H4/O, H4FO, HIST4H4) histone-H2A histone-H2B histone-H3