Chromatin compaction

Acetylation of the histone tails correlates with the activities of genes (Kimura et al., 2005). However, the detailed analyses of the acetylation on the individual lysine residue have revealed that the relationship between the acetylation and the chromatin-compaction is not simple. There are 1-6 lysine residues in each histone subunit, that could be acetylated the Lys of H2A, Lys, Lys, Lys, and Lys ° ofH2B, Lys , Lys , Lys, Lys, Lys, andLys of H3, and Lys, Lys, Lys, and Lys of H4. In mammal, more than ten HATs (7/istone Acetyl Transferases) have been identified, each of which acetylates a specific lysine residue. Acetylation frequently occurs in euchromatin regions, and some in heterochromatin regions. For example, the acetylation of Lys of H4 leads to a telomeric silencing (Kelly et al., 2000). In Drosophila, Lys of H4 is acetylated specifically in the... 

Ding HF, Bustin M, Hansen U (1997) Alleviation of histone Hl-mediated transcriptional repression and chromatin compaction by the acidic activation region in chromosomal protein HMG-14. Mol Cell Biol 17 5843-5855... 

The Role of PARP-1 as a Specific Nucleosome-Binding Factor Effects on Chromatin Compaction and Chromatin-dependent Transcription... 

Figure 4. Visualization of PARP-1-mediated chromatin compaction by atomic force microscopy. Chromatin assembled in vitro on a circular 10.5kb plasmid DNA was purified, incubated widi or without recombinant human PARP-1, and imaged by atomic force microscopy. Two types of images are shown scan probe oscillation amplitude (top) and topography (bottom height scale is indicated). The length scale is indicated. (See Colour Plate 6.)...

Histone H2B amino-terminal tail is essential for chromatin condensation (de la Barre et al, 2001). In Xenopus, chicken, and human cells phosphorylation of H2B at Serine 14 by Mstl (Mammalian Sterile Twenty) kinase has been finked to chromatin compaction during apoptosis (Ajiro, 2000 Cheung et al, 2003), and DNA double-strand breaks (Fernandez-Capetillo et al, 2004) (Fig. 2) (Table 1). At late time points after irradiation, phosphorylated H2B (S14) accumulates into... 

A second model for HMGN action is that it counteracts chromatin compaction by linker histones. The ability of HMGN proteins to unfold SV40 minichromosomes and stimulate transcription from them is dependent on the presence of linker histones, and the data is consistent with HMGN counteracting the repressive... 

Since linker histones are involved in compacting the chromatin fiber, it was of interest to see whether the methylation-mediated chromatin compaction could be explained by a higher affinity of linker histones for methylated DNA. The literature on this point is highly controversial some reports demonstrated strong preference of linker histones for methylated DNA [168,169] whereas others found that linker histone binding was indifferent to the methylation status of the DNA [164,170,171]. 

The possible structural involvement of linker histones in the methylation-mediated chromatin condensation has been recently addressed by using the Atomic Force Microscope [175]. This extensive study combined in vivo and in vitro approaches to demonstrate that DNA methylation could cause chromatin compaction only in co-operation with linker histone binding. Finally, it may be... 

Inactive and active chromatin domains can be defined at the molecular level by the presence (or absence) of specific histone modifications (or combinations of modifications), by the degree of chromatin compaction and the presence of chromatin associated proteins. Several earlier studies focusing on specific genes or loci showed that active chromatin is generally more accessible and enriched in acetylated forms of histones H3, H4, H2A [5] and histone H3 methylated at lysine 4 (H3/K4) [6]. H3/K4 di- and tri-methylation and H 3 acetylation correlate globally with open chromatin [7]. 

C.J. Hirst, M. Herlyn, RA. Cattini, and E. Kardami, High levels of CUG-initiated FGF-2 expression cause chromatin compaction, decreased cardiomyocyte mitosis, and cell death, Mol Cell Biochem 246, 111-116(2003). 

Mild convolution Chromatin compaction and margination. 1 Condensation of cytoplasm... 

Chromatin compaction - Wrapping DNA about histone cores to form nucleosomes (see here) accomplishes part of the compaction necessary to fit the long eukaryotic DNA into the nucleus. However, much of the chromatin in the nucleus is even more highly compacted. The next stage in compaction involves folding the beaded fiber into a thicker fiber like that shown in Figure 28.12. These fibers may be further folded on themselves to make the thicker chromatin fibers visible in both metaphase chromosomes and the nuclei of nondividing (interphase) cells. 

The different spatial distribution of genes in the nucleus and the different chromatin compaction arc apparently general for all vertebrates, as expected from our previous comparative investigations, and as shown by results on Raua escuienta (Fig, 7,28),... 

Filipski J. (1987). Correlation between molecular clock ticking, codon usage fidelity of DNA repair, chromosome banding and chromatin compactness in germline cells. FEES Lett. 217 184-186. 

What exactly this fiber folds into is—remarkably—not known. A great variety of EM and other approaches— dutifully represented in textbook schematics—have suggested that the next level of chromatin compaction is an entity termed the 30-nm fiber. In 1979, F. Thoma, A. KoUer, and A. Klug proposed a model for this entity ac-... 

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