Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.31.1 (micrococcal nuclease)
 2,818 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cell death by apoptosis mediates several important physiologic and pathologic processes and appears to be intrinsically programmed. Its characteristic features are distinctive morphologic changes of nucleus and cytoplasm, along with cleavage of chromatin at regularly spaced sites. Here we study DNA organization and nuclear structure in apoptotic thymocytes to define the cleavage event and, by implication, the role of the responsible endonuclease. We show that in apoptosis, double-stranded cleavage of DNA generates two classes of chromatin fragments: 70% of DNA exists as long, H1-rich oligonucleosomes bound to the nucleus, and 30% comprises short oligonucleosomes and mononucleosomes, which are depleted in H1, enriched in HMG1 and 2, and not attached to the nucleus. This minority class probably derives from chromatin in a transcriptionally active configuration, which would allow better access to enzymes in the nucleoplasm, producing more complete digestion. The characteristic nucleolar morphology in apoptosis can also be explained in terms of cleavage of the transcriptionally active ribosomal genes, with conservation of the nucleolin-rich fibrillar center. The chromatin cleavage, nucleolar morphologic changes, and chromatin condensation were closely mimicked by micrococcal nuclease digestion of normal thymocyte nuclei in the presence of protease inhibitors. Thus, in apoptosis, selective activation of an endogenous endonuclease appears to be responsible not only for widespread chromatin cleavage but also for the major nuclear morphologic changes.
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PMID:Apoptosis. The role of the endonuclease. 215 31

In cell-free translations of RNA from primary cultures of pig trachea surface epithelial cells we observed that a mRNA encoding a 20 kDa proline-rich protein (sPRP) was dramatically induced during culturing (Tesfaigzi et al., 1990, Biochem. Biophys. Res. Commun., 172:M1304-1309). This mRNA was not detected in tracheal tissue or in epithelial cells prior to culturing. Antisera were raised to synthetic peptide sequences corresponding to 23 amino acids on the C-terminus (C23-antiserum) and 29 amino acids on the N-terminus (N29 antiserum) of sPRP. On Western blot analysis, C23 antiserum reacted with a 20 kDa protein in cytosolic extracts from pig tracheal cells maintained in culture for 4 days. The reaction with the 20 kDa protein was inhibited by adding C23 peptide. Two nuclear proteins (66 and 70 kDa) obtained by micrococcal nuclease treatment of tracheal cell nuclei were detected on Western blots with C23 antiserum. These proteins were present in cells both before and after culturing. Sucrose gradient fractionation indicated that these nuclear proteins are associated with chromatin. Small amounts of the 66 and 70 kDa proteins were obtained from nuclear matrix fractions. These nuclear proteins also reacted with N29 antiserum. Since these proteins share similar epitopes with the N- and C-termini of sPRP, it is likely that the 20 kDa protein (sPRP) is part of these proteins. However, purification of the nuclear proteins followed by an amino acid sequence analysis is necessary to clarify whether sPRP is part of these proteins.
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PMID:Two nuclear proteins in tracheal epithelial cells are recognized by antibodies specific to a squamous differentiation marker, sprI. 765 64

Most DNA topoisomerase II (topo II) in cell-free extracts of 0-2-h old Drosophila embryos appears to be nonnuclear and remains in the supernatant after low-speed centrifugation (10,000 g). Virtually all of this apparently soluble topo II is particulate with a sedimentation coefficient of 67 S. Similar topo II-containing particles were detected in Drosophila Kc tissue culture cells, 16-19-h old embryos and extracts of progesterone-matured oocytes from Xenopus. Drosophila topo II-containing particles were insensitive to EDTA, Triton X-100 and DNase I, but could be disrupted by incubation with 0.3 M NaCl or RNase A. After either disruptive treatment, topo II sedimented at 9 S. topo II-containing particles were also sensitive to micrococcal nuclease. Results of chemical cross-linking corroborated those obtained by centrifugation. Immunoblot analyses demonstrated that topo II-containing particles lacked significant amounts of lamin, nuclear pore complex protein gp210, proliferating cell nuclear antigen, RNA polymerase II subunits, histones, coilin, and nucleolin. Northern blot analyses demonstrated that topo II-containing particles lacked U RNA. Thus, current data support the notion that nonnuclear Drosophila topo II-containing particles are composed largely of topo II and an unknown RNA molecule(s).
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PMID:An RNase-sensitive particle containing Drosophila melanogaster DNA topoisomerase II. 808 68

Herpesvirus nucleocapsids assemble in the nucleus and must cross the nuclear membrane for final assembly and maturation to form infectious progeny virions in the cytoplasm. It has been proposed that nucleocapsids enter the perinuclear space by budding through the inner nuclear membrane, and these enveloped nucleocapsids then fuse with the outer nuclear membrane to enter the cytoplasm. Little is known about the mechanism(s) for nuclear egress of herpesvirus nucleocapsids and, in particular, which, if any, cellular proteins are involved in the nuclear egress pathway. UL12 is an alkaline nuclease encoded by herpes simplex virus type 1 (HSV-1) and has been suggested to be involved in viral DNA maturation and nuclear egress of nucleocapsids. Using a live-cell imaging system to study cells infected by a recombinant HSV-1 expressing UL12 fused to a fluorescent protein, we observed the previously unreported nucleolar localization of UL12 in live infected cells and, using coimmunoprecipitation analyses, showed that UL12 formed a complex with nucleolin, a nucleolus marker, in infected cells. Knockdown of nucleolin in HSV-1-infected cells reduced capsid accumulation, as well as the amount of viral DNA resistant to staphylococcal nuclease in the cytoplasm, which represented encapsidated viral DNA, but had little effect on these viral components in the nucleus. These results indicated that nucleolin is a cellular factor required for efficient nuclear egress of HSV-1 nucleocapsids in infected cells.
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PMID:Nucleolin is required for efficient nuclear egress of herpes simplex virus type 1 nucleocapsids. 1995 12