Chromatin Chromosomes

Binding of nitroso-procainamide to histone proteins may perturb chromatin structure or catabolism, resulting in immunogenic forms of DNA-free histones. In fact, all sera of patients (n = 24) with procainamide-induced Lupus showed IgG and IgM antibody activity against various histone components of chromatin (chromosome subunits)122. The nature of the procainamide adduct to histone proteins still awaits elucidation. 

SNF2h/cohesin/ hSnfZh hRAD21 SMCl, SMC3, SA1/SA2, Loading of cohesion complex components onto chromatin, chromosome... 

The Physical Organization of Eukaryotic DNA Chromosomes and Chromatin Chromosomes Chromatin (Table 28.1)... 

Bonner, J., Dahmus, M. E., Fambrough, D., Huang, R.-C. C., Marushige, K., Tuan, D. Y. H. (1) The biology of isolated chromatin. Chromosomes, biologically active in the test tube, provide a powerful tool for the study of gene action. Science 159, 47—56 (1968). 

Imaging/Labeiing Applications Nucleic acids cells chromatin chromosomes ... 

The native form of chromatin in cells assumes a higher order stmcture called the 30-nm filament, which adopts a solenoidal stmcture where the 10-nm filament is arranged in a left-handed cod (Fig. 5). The negative supercoiling of the DNA is manifested by writhing the hehcal axis around the nucleosomes. Chromatin stmcture is an example of toroidal winding whereas eukaryotic chromosomes are linear, the chromatin stmctures, attached to a nuclear matrix, define separate closed-circular topological domains. 

Nucleus The nucleus is separated from the cytosol by a double membrane, the nuclear envelope. The DNA is complexed with basic proteins (histones) to form chromatin fibers, the material from which chromosomes are made. A distinct RNA-rich region, the nucleolus, is the site of ribosome assembly. The nucleus is the repository of genetic information encoded in DNA and organized into chromosomes. During mitosis, the chromosomes are replicated and transmitted to the daughter cells. The genetic information of DNA is transcribed into RNA in the nucleus and passes into the cytosol where it is translated into protein by ribosomes. 

The DNA in a eukaryotic cell nucleus during the interphase between cell divisions exists as a nucleoprotein complex called chromatin. The proteins of chromatin fall into two classes histones and nonhistone chromosomal proteins. 

CHROMATIN IS THE CHROMOSOMAL MATERIAL EXTRACTED FROM NUCLEI OF CELLS OF EUKARYOTIC ORGANISMS... 

Gertain cells of insects, eg, Chironomus, contain giant chromosomes that have been repficated for ten cycles without separation of daughter chromatids. These copies of DNA fine up side by side in precise register and produce a banded chromosome containing regions of condensed chromatin and fighter bands of... 

Uncultured cells have also been used to a limited extent for fetal sex determination. This Is possible because the cells can be appropriately stained and examined for the presence of sex chromatin, characteristic of female cells, and for the fluorescent Y-body, characteristic of male cells (33,34). However, these cytologic techniques are not completely reliable, and It Is still desirable to determine fetal sex by direct chromosome analysis (35). 

The non-cleavage pathway would remove most cohesin during prophase/ pro-metaphase by an as yet obscure mechanism. This pathway could involve phosphorylation of a cohesin subunit by mitotic protein kinases, because vertebrate cohesins rebind to chromatin in telophase when mitotic kinases are inactivated and chromosomes decondense (Losada et al 1998). The dissociation of cohesin from chromatin during prophase coincides with, but does not depend on, the association of condensin with chromosomes. This first phase of cohesin removal may be crucial (possibly along with the arrival of... 

Hie chromatinic structures in E. coli from old cultures were too small to be resolved accurately. After transfer to fresh medium the chromatinic structures increased in size and gave rise to short, often dumbbell-shaped rods or chromosomes, which multiplied by splitting lengthwise in a plane more or less parallel to the short axis of the cell. A single cell of E. coli contained one chromatinic body or one or two pairs of these representing primary and secondary division products. 

The chromosome structure is visible only during the mitotic portion of the cell cycle. The constituent parts of the chromosomes are nucleoprotein fibers called chromatin. When condensed, chromatin forms a microscop-ically visible chromosome-like structure. The chromosomes are composed of DNA, RNA, and proteins. The relative amounts of the three vary, but chromatin is primarily protein and DNA. 

The nucleus contains a large number of proteins other than histones. These so-called nonhistone proteins may or may not be tightly associated with the chromosomes. For example, the nucleus contains enzymes associated with the synthesis of RNA and DNA these are nonhistone proteins, but they are not part of the structure of chromosomes. One group of nonhistone proteins are the high mobility group (HMG) proteins, named for their rapid movement on polyacryl-amide gel electrophoresis. The HMG proteins, but not histone HI, are associated with the chromatin that is most active in RNA synthesis. 

Orlando, V. (2000) Mapping chromosomal proteins in vivo by formaldehyde-crosslinked-chromatin immunoprecipitation. Trends Biochem. Sci. 3, 99-104. 

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