Chromatin condensation

The antagonist-induced conformation of nuclear hormone receptors attracts co-repressors like Nco/SMRT (nuclear hormone receptor co-repressor/silencing mediator of retinoid and thyroid receptors) which further recruit other nuclear proteins with histone deacetylase activity. Their action leads to chromatin condensation, thus preventing the general transcription apparatus from binding to promoter regions. 

DNA fragmentation occurs in two stages. Firstly, endonucleolytic activity cleaves the DNA into high molecular weight fragments leading to the morphological picture of chromatin condensation characteristic... 

Pyknosis refers to a degenerative (thickening) process in a cell in which the nucleus shrinks in size and chromatin condenses to a solid mass that has no defined structure. 

Another morphological assay of apoptosis is done with acridine orange, a nuclear staining that reveals chromatin condensation under light and fluorescent microscope. 

Borsuk E, Manka R 1988 Behavior of sperm nuclei in intact and bisected metaphase II mouse oocytes fertilized in the presence of colcemid. Gamete Res 20 365-376 Ciemerych MA 1995 Chromatin condensation activity and cortical activity during the first three cell cycles of mouse embryo. Mol Reprod Dev 41 416—424 Ciemerych MA, Kubiak JZ 1999 Transient reactivation of CSF in parthenogenetic one-cell mouse embryos. Biol Cell 91 641—647... 

A widely used criterion for identifying a cell as apoptotic is nuclear chromatin condensation and fragmentation 611... 

Maintenance of organellar integrity Maintenance of ATP levels Maintenance of ion homeostasis Membrane surface blebbing Nuclear chromatin condensation/fragmentation Requires synthesis of death effector proteins Prevented by blocking steps in the death cascade Does not adversely affect neighbor cells... 

Another group of non-histone proteins have been identified as essential components for the formation of the condensed chromosome (Table 1). Topoisomerase II (topo II) localizes in the scaffold/matrix fraction of the interphase nuclear (Berrios et al., 1985) and the mitotic chromosome (Maeshima and Laemmli, 2003) (see section 3.1). Topo II forms a ring-shaped homodimer (Berger et al, 1996 Nettikadan et al, 1998) and catalyzes the decatenation and relaxation of DNA double strand (Wang, 2002). In fission yeast, chromosomes cannot be condensed without functional topo II (Uemura et al, 1987). In addition, in in vitro experiment, mitotic extracts containing topo II induce chromatin condensation in the isolated nuclei from HeLa and chicken erythrocyte cells (Adachi et al., 1991). 

Phosphorylation has been thought to be correlated to the mitotic chromatin condensation and the transcriptional regulation in interphase (Nowak and Corces, 2004). The mitotic phosphorylation, which was first identified in 1978 (Gurley et al, 1978), occurs at Ser (Wei et al, 1998), Ser (Goto et al, 1999), and Thr (Preuss et al, 2003) in histone H3. The Ser phosphorylation is catalyzed by the aurora kinase family (de la Barre et al, 2000), and is required for the initiation of chromosome condensation but not for its maintenance (dephosphorylation of mitotic chromosomes does not induce chromosome decondensation) (Van Hooser et fl/.,1998). In meiosis, Ser phosphorylation is also required for the cohesion of sister chromatids rather than the condensation (Kaszas and Cande, 2000). 

Shen X, Yu L, Weir JW, Gorovsky MA (1995) Linker histones are not essential and affect chromatin condensation in vivo. Cell 82 47—56... 

Verschure PJ, van der Kraan I, de Leeuw W, van der Vlag J, Carpenter AE, Belmont AS, van Driel R (2005) In vivo HPl targeting causes large-scale chromatin condensation and enhanced histone lysine methylation. Mol Cell Biol 25 4552-4564... 

Hofmann N, Hilscher B (1991) Use of aniline blue to assess chromatin condensation in morphologically normal spermatozoa in normal and infertile men. Hum Reprod 6 979-982 Howman EV, Fowler KJ, Newson AJ, Redward S, MacDonald AC, Kalitsis P, Choo KH (2000) Early disruption of centromeric chromatin organization in centromere protein A (Cenpa) null mice. Proc Natl Acad Sci U S A 97 1148-1153... 

H3-H4 Chaperone activity during rapid replication in early embryogenesis Sperm decondensation Chromatin condensation during apoptosis... 

Cross-linkers, Chromatin condensation. Histone tails, Nucleosome phasing... 

EFFECT OF REVERSIBLE DNA-BINDING OF ANTIBIOTICS UPON CHROMATIN CONDENSATION... 

The ability of DNA-binding drugs to induce chromatin condensation calls for in-depth studies, because the biological consequence of chromatin condensation is its loss of transcriptional ability. Therefore it might be a mechanism of transcription inhibition by the reversible DNA binders. The first report in this line (Sen and Crothers, 1986) employed transient electric dichroism to study the ability of the drugs to induce folding of chromatin from the 10- to 30-nm fiber either by... 

Lohse J, Dahl O, Neilsen PE (1999) Double duplex invasion by peptide nucleic acid a general principle for sequence-specific targeting of double stranded DNA. Proc Natl Acad Sci USA 96 11804-11808 Lonn U, Lonn S, Nylen U, Windblad G (1990) Bleomycin-induced DNA lesions are dependent on nucleosome repeat length. Biochem Pharmacol 39(1) 101-107 Lopez-Larraza DM, Bianchi NO (1993) DNA response to bleomycin in mammalian cells with variable degrees of chromatin condensation. Environ Mol Mutagen 21(3) 258—264 Lopez-Larraza DM, Padron J, Rond NE, Vidal Rioja LA (2006) Chromatin condensation and differential sensitivity of mammalian and insect cells to DNA strand breaks induced by bleomycin. Mutat Res 16 April [Epub ahead of print]... 

Seenisamy J, Bashyam S, Gokhale V, Vankayalapati H, Sun D, Siddiqui-Jain A, Streiner N, Shin-Ya K, White E, Wilson WD, Hurley EH (2005) Design and synthesis of an expanded porphyrin that has selectivity for the c-MYC G-quadruplex structure. J Am Chem Soc 127(9) 2944-2959 Sen D, Crothers DM (1986) Influence of DNA-binding drugs on chromatin condensation. Biochemistry 25(7) 1503-1509... 

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... 

N-terminal methylation of proteins is possible and can play a major role in mitosis. Chen etal. discovered that the N-terminal serine or proline of regulator of chromatin condensation 1 (RCCl) is methylated. RCCl associates with chromatin, binding to histones H2 A and H2B, regulated by Ran, a GTPase. " For methylation to occur, the initiating methionine must be removed and a proline and lysine must be at positions 3 and 4, respectively. If RCCl is N-terminal methylation deficient, its binding to histones loses efficiency, which can cause spindle pole defects and ultimately cause problems in cell division. This work suggests the first known function for N-terminal protein methylation. ... 

Transcription regulators are also known to be sumoylated. One of tbe early studies of tbis phenomenon showed that promyelocytic leukemia protein (PML) is a substrate for SUMO conjugation. Once SUMO is attached to the PML protein it is directed to a subdomain of tbe nucleus called tbe PML oncogenic domain (POD). It is thought that POD localization of the PML protein allows it to recruit other proteins such as transcription factors. Transcription factors in the POD can activate or inhibit transcription. Another transcription factor known to be sumoylated is Sp3. ° SUMO also has roles in chromatin condensation and interphase chromosome organization. ... 

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