| ribonucleoproteins, small nuclear | Highly conserved nuclear RNA-protein complexes that function in RNA processing in the nucleus, including pre-mRNA splicing and pre-mRNA 3'-end processing in the nucleoplasm. The u3 snrnp is localised in the nucleolus, where it aligns into base pairs with the 28s rrna precursor in a still unidentified region and functions in pre-rrna processing. The u7 snrnp aligns into base pairs with a conserved sequence in the 3'-end of histone pre-mRNA and is an essential cofactor for the cleavage that creates the mature nonadenylated 3'-end. (12 Dec 1998) |
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| ribonucleoproteins, small, u1 | A nuclear RNA-protein complex that plays a role in RNA processing. In the nucleoplasm, the u1 snrnp along with other small ribonucleoproteins (u2, u4-u6, and u5) assemble into spliceosomes that remove introns from pre-mRNA by splicing. The u1 snrnp base pairs with conserved sequence motifs at the 5'-splice site and recognises both the 5'- and 3'-splice sites and may have a fundamental role in aligning the two sites for the splicing reaction. (12 Dec 1998) |
| ribonucleoproteins, small, u2 | A nuclear RNA-protein complex that plays a role in RNA processing. In the nucleoplasm, the u2 snrnp along with other small ribonucleoproteins (u1, u4-u6, and u5) assemble into spliceosomes that remove introns from pre-mRNA by splicing. The u2 snrnp base pairs with conserved sequence motifs at the branch point, which associates with a heat- and rnaase-sensitive factor in an early step of splicing. (12 Dec 1998) |
| ribonucleoproteins, small, u4-u6 | A nuclear RNA-protein complex that plays a role in RNA processing. In the nucleoplasm, the u4-u6 snrnp along with the u5 snrnp preassemble into a single 25s particle that binds to the u1 and u2 snrnps and the substrate to form mature spliceosomes. There is also evidence for the existence of individual u4 or u6 snrnps in addition to their organization as a u4-u6 snrnp. (12 Dec 1998) |
| ribonucleoproteins, small, u5 | A nuclear RNA-protein complex that plays a role in RNA processing. In the nucleoplasm, the u5 snrnp along with u4-u6 snrnp preassemble into a single 25s particle that binds to the u1 and u2 snrnps and the substrate to form mature spliceosomes. (12 Dec 1998) |
| ribonucleoproteins | Proteins conjugated with ribonucleic acids (RNA) or specific RNA. Many viruses are ribonucleoproteins. (12 Dec 1998) |
| antibodies, antineutrophil cytoplasmic | Autoantibodies directed against cytoplasmic constituents of polymorphonuclear leukocytes and/or monocytes. They are used as specific markers for wegener's granulomatosis and other diseases, though their pathophysiological role is not clear. Anca are routinely detected by indirect immunofluorescence with three different patterns: c-anca (cytoplasmic), p-anca (perinuclear), and atypical anca. (12 Dec 1998) |
| receptors, cytoplasmic and nuclear | Proteins in the cytoplasm or nucleus that specifically bind signalling molecules and trigger changes which influence the behaviour of cells. The major groups are the steroid hormone receptors, which usually are found in the cytoplasm, and the thyroid hormone receptors, which usually are found in the nucleus. Receptors, unlike enzymes, generally do not catalyze chemical changes in their ligands. (12 Dec 1998) |
| cistern of cytoplasmic reticulum | See: cisterna. (05 Mar 2000) |
| cytoplasmic | Relating to the cytoplasm. (05 Mar 2000) |
| cytoplasmic antiproteinase | <chemical> An intracellular serine proteinase inhibitor; 376 amino acids, mw 38-43 kD; amino acid sequence given in first source Pharmacological action: serine proteinase inhibitors Synonym: human cap (26 Jun 1999) |
| cytoplasmic bridge | <plant biology> Thin strand of cytoplasm linking cells as in higher plants, Volvox, between nurse cells and developing eggs and between developing sperm cells. Unlike gap junctions, allows the transfer of large macromolecules. (18 Nov 1997) |
| cytoplasmic bridges | Slender cytoplasmic strands connecting adjacent cells; in histological sections of the epidermis and other stratified squamous epithelia, the bridge's are processes attached by a desmosome and are shrinkage artifacts of fixation; true bridge's with cytoplasmic confluence exist between incompletely divided germ cells. Synonym: cell bridges, cytoplasmic bridges. (05 Mar 2000) |
| cytoplasmic gene | <molecular biology> A gene which occurs outside the nucleus of an eukaryote or outside the regular chromosomes of a bacteria. (09 Oct 1997) |
| cytoplasmic granules | Stored products of a cell's metabolic activity. (12 Dec 1998) |