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Histone H1

histone h1, histone h1 antibody
Histone H1 is one of the five main histone protein families which are components of chromatin in eukaryotic cells Though highly conserved, it is nevertheless the most variable histone in sequence across species

Contents

  • 1 Structure
  • 2 Function
  • 3 Dynamics
  • 4 Isoforms
  • 5 Post-translational Modifications
  • 6 See also
  • 7 References

Structure

A diagram showing where H1 can be found in the nucleosome

Metazoan H1 proteins feature a central globular domain and long C- and short N-terminal tails H1 is involved with the packing of the "beads on a string" sub-structures into a high order structure, whose details have not yet been solved[1]

Function

Unlike the other histones, H1 does not make up the nucleosome "bead" Instead, it sits on top of the structure, keeping in place the DNA that has wrapped around the nucleosome H1 is present in half the amount of the other four histones, which contribute two molecules to each nucleosome bead In addition to binding to the nucleosome, the H1 protein binds to the "linker DNA" approximately 20-80 nucleotides in length region between nucleosomes, helping stabilize the zig-zagged 30 nm chromatin fiber[2] Much has been learned about histone H1 from studies on purified chromatin fibers Ionic extraction of linker histones from native or reconstituted chromatin promotes its unfolding under hypotonic conditions from fibers of 30 nm width to beads-on-a-string nucleosome arrays[3][4][5]

It is uncertain whether H1 promotes a solenoid-like chromatin fiber, in which exposed linker DNA is shortened, or whether it merely promotes a change in the angle of adjacent nucleosomes, without affecting linker length[6] However, linker histones have been demonstrated to drive the compaction of chromatin fibres that had been reconstituted in vitro using synthetic DNA arrays of the strong '601' nucleosome positioning element [7] Nuclease digestion and DNA footprinting experiments suggest that the globular domain of histone H1 localizes near the nucleosome dyad, where it protects approximately 15-30 base pairs of additional DNA[8][9][10][11] In addition, experiments on reconstituted chromatin reveal a characteristic stem motif at the dyad in the presence of H1[12] Despite gaps in our understanding, a general model has emerged wherein H1’s globular domain closes the nucleosome by crosslinking incoming and outgoing DNA, while the tail binds to linker DNA and neutralizes its negative charge[6][10]

Many experiments addressing H1 function have been performed on purified, processed chromatin under low-salt conditions, but H1’s role in vivo is less certain Cellular studies have shown that overexpression of H1 can cause aberrant nuclear morphology and chromatin structure, and that H1 can serve as both a positive and negative regulator of transcription, depending on the gene[13][14][15] In Xenopus egg extracts, linker histone depletion causes ~2-fold lengthwise extension of mitotic chromosomes, while overexpression causes chromosomes to hypercompact into an inseparable mass[16][17] Complete knockout of H1 in vivo has not been achieved in multicellular organisms due to the existence of multiple isoforms that may be present in several gene clusters, but various linker histone isoforms have been depleted to varying degrees in Tetrahymena, C elegans, Arabidopsis, fruit fly, and mouse, resulting in various organism-specific defects in nuclear morphology, chromatin structure, DNA methylation, and/or specific gene expression[18][19][20]

Dynamics

While most histone H1 in the nucleus is bound to chromatin, H1 molecules shuttle between chromatin regions at a fairly high rate[21][22]

It is difficult to understand how such a dynamic protein could be a structural component of chromatin, but it has been suggested that the steady-state equilibrium within the nucleus still strongly favors association between H1 and chromatin, meaning that despite its dynamics, the vast majority of H1 at any given timepoint is chromatin bound[23] H1 compacts and stabilizes DNA under force and during chromatin assembly, which suggests that dynamic binding of H1 may provide protection for DNA in situations where nucleosomes need to be removed[24]

Cytoplasmic factors appear to be necessary for the dynamic exchange of histone H1 on chromatin, but these have yet to be specifically identified[25] H1 dynamics may be mediated to some degree by O-glycosylation and phosphorylation O-glycosylation of H1 may promote chromatin condensation and compaction Phosphorylation during interphase has been shown to decrease H1 affinity for chromatin and may promote chromatin decondensation and active transcription However, during mitosis phosphorylation has been shown to increase the affinity of H1 for chromosomes and therefore promote mitotic chromosome condensation[17]

Isoforms

The H1 family in animals includes multiple H1 isoforms that can be expressed in different or overlapping tissues and developmental stages within a single organism The reason for these multiple isoforms remains unclear, but both their evolutionary conservation from sea urchin to humans as well as significant differences in their amino acid sequences suggest that they are not functionally equivalent[26][27][28] One isoform is histone H5, which is only found in avian erythrocytes, which are unlike mammalian erythrocytes in that they have nuclei Another isoform is the oocyte/zygotic H1M isoform also known as B4 or H1foo, found in sea urchins, frogs, mice, and humans, which is replaced in the embryo by somatic isoforms H1A-E, and H10 which resembles H5[28][29][30][31] Despite having more negative charges than somatic isoforms, H1M binds with higher affinity to mitotic chromosomes in Xenopus egg extracts[17]

Post-translational Modifications

Like other histones, the histone H1 family is extensively post-translationally modified PTMs This includes serine and threonine phosphorylation, lysine acetylation, lysine methylation and ubiquitination [32] These PTMs serve a variety of functions but are less well studied than the PTMs of other histones

See also

  • nucleosome
  • histone
  • chromatin
  • linker histone H1 variants
  • Other histone proteins involved in chromatin:
  • H2A
  • H2B
  • H3
  • H4

References

  1. ^ Ramakrishnan V, Finch JT, Graziano V, Lee PL, Sweet RM March 1993 "Crystal structure of globular domain of histone H5 and its implications for nucleosome binding" Nature 362 6417: 219–23 doi:101038/362219a0 PMID 8384699 
  2. ^ Jeon, Kwang W; Berezney, Ronald 1995 Structural and functional organization of the nuclear matrix Boston: Academic Press pp 214–7 ISBN 0-12-364565-4 
  3. ^ Finch JT, Klug A June 1976 "Solenoidal model for superstructure in chromatin" Proc Natl Acad Sci USA 73 6: 1897–901 doi:101073/pnas7361897 PMC 430414  PMID 1064861 
  4. ^ Thoma F, Koller T September 1977 "Influence of histone H1 on chromatin structure" Cell 12 1: 101–7 doi:101016/0092-86747790188-X PMID 561660 
  5. ^ Thoma F, Koller T, Klug A November 1979 "Involvement of histone H1 in the organization of the nucleosome and of the salt-dependent superstructures of chromatin" J Cell Biol 83 2 Pt 1: 403–27 doi:101083/jcb832403 PMC 2111545  PMID 387806 
  6. ^ a b van Holde K, Zlatanova J October 1996 "What determines the folding of the chromatin fiber" Proc Natl Acad Sci USA 93 20: 10548–55 doi:101073/pnas932010548 PMC 38190  PMID 8855215 
  7. ^ Routh, A; Sandin, S; Rhodes, D 1 July 2008 "Nucleosome repeat length and linker histone stoichiometry determine chromatin fiber structure" Proceedings of the National Academy of Sciences of the United States of America 105 26: 8872–7 doi:101073/pnas0802336105 PMC 2440727  PMID 18583476 
  8. ^ Varshavsky AJ, Bakayev VV, Georgiev GP February 1976 "Heterogeneity of chromatin subunits in vitro and location of histone H1" Nucleic Acids Res 3 2: 477–92 doi:101093/nar/32477 PMC 342917  PMID 1257057 
  9. ^ Whitlock JP, Simpson RT July 1976 "Removal of histone H1 exposes a fifty base pair DNA segment between nucleosomes" Biochemistry 15 15: 3307–14 doi:101021/bi00660a022 PMID 952859 
  10. ^ a b Allan J, Hartman PG, Crane-Robinson C, Aviles FX December 1980 "The structure of histone H1 and its location in chromatin" Nature 288 5792: 675–9 doi:101038/288675a0 PMID 7453800 
  11. ^ Staynov DZ, Crane-Robinson C December 1988 "Footprinting of linker histones H5 and H1 on the nucleosome" EMBO J 7 12: 3685–91 PMC 454941  PMID 3208745 
  12. ^ Bednar J, Horowitz RA, Grigoryev SA, Carruthers LM, Hansen JC, Koster AJ, Woodcock CL November 1998 "Nucleosomes, linker DNA, and linker histone form a unique structural motif that directs the higher-order folding and compaction of chromatin" Proc Natl Acad Sci USA 95 24: 14173–8 doi:101073/pnas952414173 PMC 24346  PMID 9826673 
  13. ^ Dworkin-Rastl E, Kandolf H, Smith RC February 1994 "The maternal histone H1 variant, H1M B4 protein, is the predominant H1 histone in Xenopus pregastrula embryos" Dev Biol 161 2: 425–39 doi:101006/dbio19941042 PMID 8313993 
  14. ^ Brown DT, Alexander BT, Sittman DB February 1996 "Differential effect of H1 variant overexpression on cell cycle progression and gene expression" Nucleic Acids Res 24 3: 486–93 doi:101093/nar/243486 PMC 145659  PMID 8602362 
  15. ^ Gunjan A, Alexander BT, Sittman DB, Brown DT December 1999 "Effects of H1 histone variant overexpression on chromatin structure" J Biol Chem 274 53: 37950–6 doi:101074/jbc2745337950 PMID 10608862 
  16. ^ Maresca TJ, Freedman BS, Heald R June 2005 "Histone H1 is essential for mitotic chromosome architecture and segregation in Xenopus laevis egg extracts" J Cell Biol 169 6: 859–69 doi:101083/jcb200503031 PMC 2171634  PMID 15967810 
  17. ^ a b c Freedman BS, Heald R June 2010 "Functional Comparison of Linker Histones in Xenopus Reveals Isoform-Specific Regulation by Cdk1 and RanGTP" Curr Biol 20 11: 1048–52 doi:101016/jcub201004025 PMC 2902237  PMID 20471264 
  18. ^ Shen X, Yu L, Weir JW, Gorovsky MA July 1995 "Linker histones are not essential and affect chromatin condensation in vivo" Cell 82 1: 47–56 doi:101016/0092-86749590051-9 PMID 7606784 
  19. ^ Jedrusik MA, Schulze E April 2001 "A single histone H1 isoform H11 is essential for chromatin silencing and germline development in Caenorhabditis elegans" Development 128 7: 1069–80 PMID 11245572 
  20. ^ Lu X, Wontakal SN, Emelyanov AV, Morcillo P, Konev AY, Fyodorov DV, Skoultchi AI February 2009 "Linker histone H1 is essential for Drosophila development, the establishment of pericentric heterochromatin, and a normal polytene chromosome structure" Genes Dev 23 4: 452–65 doi:101101/gad1749309 PMC 2648648  PMID 19196654 
  21. ^ Misteli T, Gunjan A, Hock R, Bustin M, Brown DT December 2000 "Dynamic binding of histone H1 to chromatin in living cells" Nature 408 6814: 877–81 doi:101038/35048610 PMID 11130729 
  22. ^ Chen D, Dundr M, Wang C, Leung A, Lamond A, Misteli T, Huang S January 2005 "Condensed mitotic chromatin is accessible to transcription factors and chromatin structural proteins" J Cell Biol 168 1: 41–54 doi:101083/jcb200407182 PMC 2171683  PMID 15623580 
  23. ^ Bustin M, Catez F, Lim JH March 2005 "The dynamics of histone H1 function in chromatin" Mol Cell 17 5: 617–20 doi:101016/jmolcel200502019 PMID 15749012 
  24. ^ Xiao, B; Freedman, B S; Miller, K E; Heald, R; Marko, J F 2012 "Histone H1 compacts DNA under force and during chromatin assembly" Molecular Biology of the Cell 23 24: 4864–4871 doi:101091/mbcE12-07-0518 PMC 3521692  PMID 23097493 
  25. ^ Freedman BS, Miller KE, Heald R 2010 Cimini D, ed "Xenopus Egg Extracts Increase Dynamics of Histone H1 on Sperm Chromatin" PLoS ONE 5 9: e13111 doi:101371/journalpone0013111 PMC 2947519  PMID 20927327 
  26. ^ Steinbach OC, Wolffe AP, Rupp RA September 1997 "Somatic linker histones cause loss of mesodermal competence in Xenopus" Nature 389 6649: 395–9 doi:101038/38755 PMID 9311783 
  27. ^ De S, Brown DT, Lu ZH, Leno GH, Wellman SE, Sittman DB June 2002 "Histone H1 variants differentially inhibit DNA replication through an affinity for chromatin mediated by their carboxyl-terminal domains" Gene 292 1–2: 173–81 doi:101016/S0378-11190200675-3 PMID 12119111 
  28. ^ a b Izzo A, Kamieniarz K, Schneider R April 2008 "The histone H1 family: specific members, specific functions" Biol Chem 389 4: 333–43 doi:101515/BC2008037 PMID 18208346 
  29. ^ Khochbin S June 2001 "Histone H1 diversity: bridging regulatory signals to linker histone function" Gene 271 1: 1–12 doi:101016/S0378-11190100495-4 PMID 11410360 
  30. ^ Godde JS, Ura K March 2008 "Cracking the enigmatic linker histone code" J Biochem 143 3: 287–93 doi:101093/jb/mvn013 PMID 18234717 
  31. ^ Happel N, Doenecke D February 2009 "Histone H1 and its isoforms: contribution to chromatin structure and function" Gene 431 1–2: 1–12 doi:101016/jgene200811003 PMID 19059319 
  32. ^ Harshman SW, Young NL, Parthun MR, Freitas MA August 2013 "H1 histones: current perspectives and challenges" Nucleic Acids Res 21 41: 9593–609 doi:101093/nar/gkt700 PMID 23945933 

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Histone H1


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    29.10.2014


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