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Chromatin compaction in terminally differentiated avian blood cells: the role of linker histone H5 and non-histone protein MENT.

Kowalski A, Pałyga J - Chromosome Res. (2011)

Bottom Line: Chromatin has a tendency to shift from a relatively decondensed (active) to condensed (inactive) state during cell differentiation due to interactions of specific architectural and/or regulatory proteins with DNA.These highly abundant proteins assist in folding of nucleosome arrays and self-association of chromatin fibers into compacted chromatin structures.Here, we briefly review structural aspects and molecular mode of action by which these unrelated proteins can spread condensed chromatin to form inactivated regions in the genome.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Genetics, Institute of Biology, Jan Kochanowski University, ul. Świętokrzyska 15, 25-406 Kielce, Poland. a.kowalski@ujk.kielce.pl

ABSTRACT
Chromatin has a tendency to shift from a relatively decondensed (active) to condensed (inactive) state during cell differentiation due to interactions of specific architectural and/or regulatory proteins with DNA. A promotion of chromatin folding in terminally differentiated avian blood cells requires the presence of either histone H5 in erythrocytes or non-histone protein, myeloid and erythroid nuclear termination stage-specific protein (MENT), in white blood cells (lymphocytes and granulocytes). These highly abundant proteins assist in folding of nucleosome arrays and self-association of chromatin fibers into compacted chromatin structures. Here, we briefly review structural aspects and molecular mode of action by which these unrelated proteins can spread condensed chromatin to form inactivated regions in the genome.

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Models for the formation of compacted chromatin fibers. a A formation of dense chromatin structure by histone H5-mediated association of adjacent nucleosomes and bridging of distant nucleosome chains. A side-by-side self-association of compacted neighboring poly-nucleosome arrays may facilitate further chromatin condensation. b Two-step formation of compacted chromatin fibers by initial binding of MENT-monomers to DNA and folding the nucleosome arrays and subsequent self-association of the chromatin fibers by MENT-oligomers
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Fig2: Models for the formation of compacted chromatin fibers. a A formation of dense chromatin structure by histone H5-mediated association of adjacent nucleosomes and bridging of distant nucleosome chains. A side-by-side self-association of compacted neighboring poly-nucleosome arrays may facilitate further chromatin condensation. b Two-step formation of compacted chromatin fibers by initial binding of MENT-monomers to DNA and folding the nucleosome arrays and subsequent self-association of the chromatin fibers by MENT-oligomers

Mentions: Histone H5 replacing histone H1 in mature erythrocytes constituted about 60% of the total amount of linker histones (Koutzamani et al. 2002). Exchange of H1 by H5 prevented the mobility of nucleosomes (Pennings et al. 1994) resulting in a greater stability of chromatin (Bates and Thomas 1981) so that the histone H5 is regarded to be more potent factor in producing extensively repressed regions in the erythroid genome. A microinjection of H5 into proliferating myoblasts generated a densely compacted chromatin in the injected cells compatible with the inhibition of transcription and replication (Bergman et al. 1988). A similar repressive effect was observed after expression of histone H5 in rat sarcoma cells transfected with MMTV-H5 constructs (Sun et al. 1990). A higher binding affinity of histone H5 compared to H1 subtypes (Orrego et al. 2007) could explain a greater ability of the H5 to produce more compacted chromatin fibers in transfected rat sarcoma cells (Sun et al. 1990). Such effects may result from a better neutralization of DNA charges by the H5 due to its higher content of Arg residues. The efficiently bound nucleosomes tended to form axially stable structures similar to those in mature erythrocyte chromatin (Sun et al. 1990). Unlike the rest of linker histones, the histone H5 has a tendency to form dimers in solution by specific self-contacts within the globular domains (Carter and van Holde 1998). Using a computational docking tool for evaluation of the interaction between histone H5 globular domains, Fan and Roberts (2006) corroborated that the nucleosome dimerization was triggered by the interaction of aromatic residues between the H5 monomers (Ramakrishnan et al. 1993) which induced greater chromatin compaction by bringing the adjacent nucleosomes closer together to form zig zag structures (Rydberg et al. 1998; Bednar et al. 1998) and by connecting distant nucleosome segments to create a uniformly thick nucleosomal array (Fan and Roberts 2006) (Fig. 2a). These findings are consistent with the linker histone-induced stem formation required for chromatin folding (Bednar et al. 1998) as well as with a continuous fiber model obtained by successively stacking of tetranucleosomes one on another (Schalch et al. 2005). Moreover, the avian erythrocyte histone H5 is gradually phosphorylated after synthesis and then dephosphorylated to become fully devoid of phosphate at the terminal stage of development (Sung et al. 1977). Dephosphorylation is correlated with a strong increase in the affinity of histone H5 for DNA resulting in a sharp shift of chromatin to fully condensed state (Aubert et al. 1991).Fig. 2


Chromatin compaction in terminally differentiated avian blood cells: the role of linker histone H5 and non-histone protein MENT.

Kowalski A, Pałyga J - Chromosome Res. (2011)

Models for the formation of compacted chromatin fibers. a A formation of dense chromatin structure by histone H5-mediated association of adjacent nucleosomes and bridging of distant nucleosome chains. A side-by-side self-association of compacted neighboring poly-nucleosome arrays may facilitate further chromatin condensation. b Two-step formation of compacted chromatin fibers by initial binding of MENT-monomers to DNA and folding the nucleosome arrays and subsequent self-association of the chromatin fibers by MENT-oligomers
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3139888&req=5

Fig2: Models for the formation of compacted chromatin fibers. a A formation of dense chromatin structure by histone H5-mediated association of adjacent nucleosomes and bridging of distant nucleosome chains. A side-by-side self-association of compacted neighboring poly-nucleosome arrays may facilitate further chromatin condensation. b Two-step formation of compacted chromatin fibers by initial binding of MENT-monomers to DNA and folding the nucleosome arrays and subsequent self-association of the chromatin fibers by MENT-oligomers
Mentions: Histone H5 replacing histone H1 in mature erythrocytes constituted about 60% of the total amount of linker histones (Koutzamani et al. 2002). Exchange of H1 by H5 prevented the mobility of nucleosomes (Pennings et al. 1994) resulting in a greater stability of chromatin (Bates and Thomas 1981) so that the histone H5 is regarded to be more potent factor in producing extensively repressed regions in the erythroid genome. A microinjection of H5 into proliferating myoblasts generated a densely compacted chromatin in the injected cells compatible with the inhibition of transcription and replication (Bergman et al. 1988). A similar repressive effect was observed after expression of histone H5 in rat sarcoma cells transfected with MMTV-H5 constructs (Sun et al. 1990). A higher binding affinity of histone H5 compared to H1 subtypes (Orrego et al. 2007) could explain a greater ability of the H5 to produce more compacted chromatin fibers in transfected rat sarcoma cells (Sun et al. 1990). Such effects may result from a better neutralization of DNA charges by the H5 due to its higher content of Arg residues. The efficiently bound nucleosomes tended to form axially stable structures similar to those in mature erythrocyte chromatin (Sun et al. 1990). Unlike the rest of linker histones, the histone H5 has a tendency to form dimers in solution by specific self-contacts within the globular domains (Carter and van Holde 1998). Using a computational docking tool for evaluation of the interaction between histone H5 globular domains, Fan and Roberts (2006) corroborated that the nucleosome dimerization was triggered by the interaction of aromatic residues between the H5 monomers (Ramakrishnan et al. 1993) which induced greater chromatin compaction by bringing the adjacent nucleosomes closer together to form zig zag structures (Rydberg et al. 1998; Bednar et al. 1998) and by connecting distant nucleosome segments to create a uniformly thick nucleosomal array (Fan and Roberts 2006) (Fig. 2a). These findings are consistent with the linker histone-induced stem formation required for chromatin folding (Bednar et al. 1998) as well as with a continuous fiber model obtained by successively stacking of tetranucleosomes one on another (Schalch et al. 2005). Moreover, the avian erythrocyte histone H5 is gradually phosphorylated after synthesis and then dephosphorylated to become fully devoid of phosphate at the terminal stage of development (Sung et al. 1977). Dephosphorylation is correlated with a strong increase in the affinity of histone H5 for DNA resulting in a sharp shift of chromatin to fully condensed state (Aubert et al. 1991).Fig. 2

Bottom Line: Chromatin has a tendency to shift from a relatively decondensed (active) to condensed (inactive) state during cell differentiation due to interactions of specific architectural and/or regulatory proteins with DNA.These highly abundant proteins assist in folding of nucleosome arrays and self-association of chromatin fibers into compacted chromatin structures.Here, we briefly review structural aspects and molecular mode of action by which these unrelated proteins can spread condensed chromatin to form inactivated regions in the genome.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Genetics, Institute of Biology, Jan Kochanowski University, ul. Świętokrzyska 15, 25-406 Kielce, Poland. a.kowalski@ujk.kielce.pl

ABSTRACT
Chromatin has a tendency to shift from a relatively decondensed (active) to condensed (inactive) state during cell differentiation due to interactions of specific architectural and/or regulatory proteins with DNA. A promotion of chromatin folding in terminally differentiated avian blood cells requires the presence of either histone H5 in erythrocytes or non-histone protein, myeloid and erythroid nuclear termination stage-specific protein (MENT), in white blood cells (lymphocytes and granulocytes). These highly abundant proteins assist in folding of nucleosome arrays and self-association of chromatin fibers into compacted chromatin structures. Here, we briefly review structural aspects and molecular mode of action by which these unrelated proteins can spread condensed chromatin to form inactivated regions in the genome.

Show MeSH
Related in: MedlinePlus