The morphology of chromosomes (certain rod-shaped structures) is highly reproducible despite the high condensation of chromatin fibers (∼1 mm) into chromosomes (∼1 μm). However, the mechanism underlying the condensation of chromatin fibers into chromosomes is unclear. We assume that investigation of the internal structure of chromosomes will aid in elucidating the condensation process. In order...

Epigenetics refers to the study of heritable changes in gene expression that do not depend on the DNA sequence itself. Those changes alter the phenotype without any change in the genotype and can be influenced by several factors. The environment, the way of living, habits, age, parental nutritional state during gestation and others are amongst the major factors influencing chromatin remodeling....

Chromatin recently emerged as one of the governing factors for self-renewal and pluripotency of embryonic stem (ES) cells. Stem cell chromatin is distinct from that of somatic or differentiated cells in several different structural and functional aspects including chromatin modifications, global chromatin arrangement and condensation and compaction of chromosome territories. Live imaging method...

The binding of fluorescently tagged proteins to tandem DNA arrays has been instrumental in understanding nuclear organization and function. Through the use of more natural tandem DNA arrays, Hu et al. (Hu, Y., I. Kireev, M. Plutz, N. Ashourian, and A.S. Belmont. 2009. J. Cell Biol. 185:87-100) gain new insights into chromatin organization and dynamics, and into the association of splicing facto...

Background During mammalian spermatogenesis unique and dynamic epigenetic events occur leading to chromatin condensation. Through these events, histone demethylases such as JMJD1A play important roles in compaction of sperm chromatin, due to regulation of histone methylation dynamics and alteration of chromatin structure. As �histone methylation� is one of the best-characterized modifications i...

Chl1 DNA helicase promotes sister chromatid cohesion and associates with both the cohesion establishment acetyltransferase Eco1/Ctf7 and the DNA polymerase processivity factor PCNA that supports Eco1/Ctf7 function. Mutation in CHL1 results in precocious sister chromatid separation and cell aneuploidy, defects that arise through reduced levels of chromatin-bound cohesins which normally tether to...

Increased amounts of chromatin condensation (i.e., localized areas of high DNA density, or chromatin higher order packing state) have been described in NIH 3T3 cells transformed with the Ha-ras oncogene. The structural basis for this oncogene-mediated alteration in nuclear organization is unknown. Since DNA methylation is likely to be involved in regulating the nucleosomal level of DNA packagin...

We have developed an in vitro system in which higher-order chromatin structures are assembled around naked DNAs in a cell cycle-dependent manner. Membrane-free soluble extracts specific to interphase and mitotic states were prepared from Xenopus eggs. When high molecular weight DNA is incubated with interphase extracts, fluffy chromatin-like structures are assembled. In contrast, mitotic extrac...

Previous studies have implicated histone H5 dephosphorylation as a causal factor in genetic inactivation and chromatin condensation during erythroid senescence in adult chickens. We show that histone H5 phosphorylation declines in two stages as various cohorts of erythroid cells senesce in chick embryos. The first decline occurs between 5 and 6 days and coincides with the senescence of primitiv...

The processes underlying the large-scale reorganisation of chromatin in mitosis that form compact mitotic chromosomes and ensure the fidelity of chromosome segregation during cell division still remain obscure. The chromosomal condensin complex is a major molecular effector of chromosome condensation and segregation in diverse organisms ranging from bacteria to humans. Condensin is a large, evo...