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Linker histone subtype composition and affinity for chromatin in situ in nucleated mature erythrocytes
Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
Institute of Medical Chemistry and Biochemistry, University of Innsbruck, Innsbruck, Austria .
Institute of Medical Chemistry and Biochemistry, University of Innsbruck, Innsbruck, Austria .
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2002 (English)In: Journal of Biological Chemistry, ISSN 0021-9258, Vol. 277, no 47, 44688-44694 p.Article in journal (Refereed) Published
Abstract [en]

The replacement linker histones H10 and H5 are present in frog and chicken erythrocytes, respectively, and their accumulation coincides with cessation of proliferation and compaction of chromatin. These cells have been analyzed for the affinity of linker histones for chromatin with cytochemical and biochemical methods. Our results show a stronger association between linker histones and chromatin in chicken erythrocyte nuclei than in frog erythrocyte nuclei. Analyses of linker histones from chicken erythrocytes using capillary electrophoresis showed H5 to be the subtype strongest associated with chromatin. The corresponding analyses of frog erythrocyte linker histones using reverse-phase high performance liquid chromatography showed that H10 dissociated from chromatin at somewhat higher ionic strength than the three additional subtypes present in frog blood but at lower ionic strength than chicken H5. Which of the two H10 variants in frog is expressed in erythrocytes has thus far been unknown. Amino acid sequencing showed that H10-2 is the only H10 subtype present in frog erythrocytes and that it is 100% acetylated at its N termini. In conclusion, our results show differences between frog and chicken linker histone affinity for chromatin probably caused by the specific subtype composition present in each cell type. Our data also indicate a lack of correlation between linker histone affinity and chromatin condensation.


Place, publisher, year, edition, pages
2002. Vol. 277, no 47, 44688-44694 p.
National Category
Medical and Health Sciences
URN: urn:nbn:se:liu:diva-14128DOI: 10.1074/jbc.M203533200OAI: diva2:22682
Available from: 2006-11-06 Created: 2006-11-06 Last updated: 2009-05-25
In thesis
1. Chromatin, histones, and epigenetic tags
Open this publication in new window or tab >>Chromatin, histones, and epigenetic tags
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The fundamental building blocks of chromatin are the nucleosomes. Each such unit is composed of about 200 bp of DNA, the well-conserved core histones (H2A, H2B, H3 and H4) and a linker histone (H1). The DNA is wound around two dimers of H2A–H2B and a tetramer comprising two molecules each of H3 and H4, and there is approximately one linker histone molecule positioned on the exterior of the DNA–protein octamer complex. The nucleosome directs the various structural transitions in chromatin that are needed for proper transcriptional regulation during differentiation and development of the organism in question. The gene activity can be regulated by different histone variants, DNA–protein interactions, and protein–protein interactions, all of which are influenced by the enormous amounts of post-translational modifications that occur in the histone tails. The research underlying this thesis focused on different aspects of post-translational modifications during aging, differentiation, and progression of the cell cycle, and also on expression of linker histone variants and linker histone-chromatin interactions in a variety of cells and tissues.

The present results are the first to show that H4 can be trimethylated at lysine 20 in mammalian cells. The trimethylated H4K20 was found in rat kidney and liver at levels that rose with increasing age of the nimals, and it was also detected in trace amounts in human cell lines. Furthermore, in differentiating MEL cells, trimethylated H4K20 was localized to heterochromatin, and levels of trimethylated H4K20 increased during the course of cell differentiation and were correlated with the increasing compaction of the chromatin.

The chromatin of terminally differentiated chicken and frog erythrocytes is highly condensed, and the linker histone variants it contains vary between the two species. Cytofluorometric analyses revealed that the linker histones in the chicken erythrocytes exhibited higher affinity for chromatin than did those in the frog erythrocytes. Characterization of the H1° in frog erythrocytes proved it to be the H1°-2 subvariant. Other experiments demonstrated that normal human B lymphocytes expressed the linker histone variants H1.2, H1.3, H1.4, and H1.5, and that B cells from patients with B-CLL expressed the same variants although in different amounts. The most striking dissimilarity was that amounts of H1.3 in the cells were decreased or undetectable in some samples. Sequencing did not discern any defects in the H1.3 gene, and thus the absence of H1.3 is probably regulated at the post-translational level. It was also observed that the levels of linker histone phosphorylation in EBV-transformed B lymphocytes were already increased in the G1 phase of the cell cycle, which is earlier than previously thought. This increase in phosphorylation is probably responsible for the lower affinity of linker histones for chromatin in EBV-transformed cells in the G1 phase of the cell cycle.

Place, publisher, year, edition, pages
Institutionen för biomedicin och kirurgi, 2006
Linköping University Medical Dissertations, ISSN 0345-0082 ; 960
Chromatin, histones, histone variants, epigenetics, histone H4 methylation, linker histone phosphorylation
National Category
Cell and Molecular Biology
urn:nbn:se:liu:diva-7687 (URN)91-85523-10-0 (ISBN)
Public defence
2006-10-27, Berzeliussalen, Campus US, Linköpings Universitet, Linköping, 00:00 (English)
Available from: 2006-11-06 Created: 2006-11-06 Last updated: 2009-03-04

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