Cell nucleus

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Cell nucleus

The largest of the membrane-bounded organelles which characterize eukaryotic cells; it is thought of as the control center since it contains the bulk of the cell's genetic information in the form of deoxyribonucleic acid (DNA). The nucleus has two major functions: (1) It is the site of synthesis of ribonucleic acid (RNA), which in turn directs the formation of the protein molecules on which all life depends; and (2) in any cell preparing for division, the nucleus precisely duplicates its DNA for later distribution to cell progeny. See Deoxyribonucleic acid (DNA), Eukaryotae, Ribonucleic acid (RNA)

The diameter of nuclei ranges from 1 micrometer in intracellular parasites and yeast cells to several millimeters in some insect sperm. Spherical or ellipsoidal nuclei are found in most cell types, although occasionally spindle-shaped, lobulated, disc-shaped, or cup-shaped nuclei may be observed. Although nuclear size and shape are somewhat consistent features of a particular cell type, these features are more variable in cancer cells. In addition, tumor cell nuclei are characterized by indentation, furrowing, elongation, and budding.

The nucleus is bounded by a double membrane (the nuclear envelope) and contains several major components: chromatin, which is composed of DNA and chromosomal proteins; the nucleolus, which is the site of ribosomal RNA (rRNA) synthesis; and nucleoplasmic fibrils and granules, some of which are involved in the processing and transport of messenger RNA out of the nucleus (see illustration). The constituents of the nucleus are contained within a framework referred to as the nuclear matrix.

Transmission electron micrograph of a thin section of a rat liver cell nucleusenlarge picture
Transmission electron micrograph of a thin section of a rat liver cell nucleus
References in periodicals archive ?
The pellets were then mixed with 40 [micro]g of nuclear proteins prepared from JEG-3 cells and incubated at 4[degrees]C overnight.
Distinguishing high-grade epithelial malignancies such as sinonasal undifferentiated carcinoma, undifferentiated nonkeratinizing squamous cell carcinomas including nasopharyngeal carcinoma, and nuclear protein in testis (NUT) midline carcinomas (NMCs) of the upper aerodigestive tract can be particularly difficult.
In some experiments, nuclear extracts were incubated with a 50 molar excess of unlabeled probe or an unlabeled probe from a different binding motif to examine the specificity of nuclear protein binding to the oligonucleotides.
Chemical differentiation of nuclear proteins during spermatogenesis in the salmon.
Although activated in the cytosol, the MAPKs translocate to the nucleus upon activation and phosphorylate a large number of nuclear proteins.
The resulting supernatant was used as soluble nuclear proteins.
Primarily, Cr is an essential trace element that potentiates the action of insulin and hence influences protein, lipid and carbohydrate metabolism (Nielson, 1995) including the synthesis of nuclear proteins and nucleic acid (Weser and Koolman, 1969; Okada et al.
Binding occurred with nuclear proteins from hematopoietic cells, but not with nuclear proteins from fibroblast cells.
The amount of nuclear proteins was analyzed with Lowry's method (DC protein assay; BioRad Laboratories, Hercules, CA, USA).
32]P]-labeled-oligonucleotide to nuclear proteins was inhibited completely by unlabeled oligonucleotide at 5 [Mu]g, suggesting that nuclear proteins bind specifically to the oligonucleotide (Figure 3, A and B).
Ultimately protein binding will be compared throughout the MLL bcr with the final goal of identifying potential recombination-mediating nuclear proteins.
Thyroid hormone receptors (TRs) are nuclear proteins that regulate gene expression; there are two types of TRs-[alpha] and [beta]--and there are several isoforms of each of these two types (Zhang and Lazar 2000).

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