Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have partially characterized the granules of the human NK cell line, YT-INDY, and assessed granule-mediated lysis and DNA fragmentation of assorted targets. Biochemical studies demonstrated significant quantities of granzyme B (asp-ase) and a heretofore undescribed chymase but no tryptase (i.e., granzyme A or 3) or distinct met-ase. YT-INDY expressed mRNA for granzyme B, perforin and CCPX. The existence of perforin was confirmed by immunoblot. The granules lysed both human and murine NK-sensitive and NK-resistant targets. YT-INDY and NK3.3, two human cytotoxic cells, were also lysed. EGTA reduced lysis by only 50%, suggesting that a perforin-independent lytic pathway is associated with the granules. In addition, 4-(2-aminoethyl) benzenesulfonylfluoride hydrochloride (AEBSF), an inhibitor that selectively blocked the chymase and 3,4-dichloroisocoumarin (DCI), an inhibitor that inactivated both chymase and asp-ase activities, marginally affected lysis. By gel electrophoresis and 125I-labeled deoxyuridine release assay, only murine cells (SP2/0 and YAC-1) underwent DNA fragmentation, and cleavage was completely inhibited by DCI, whereas EGTA, AEBSF and aurintricarboxylic acid (ATA) had no effect. The results, therefore, underscore the central role of granzyme B in granule-mediated DNA fragmentation, emphasize that the protease acts via an ATA-resistant endonuclease pathway and stress that nucleolysis does not invariably accompany granule-mediated cytolysis. Finally, ATA inhibited the asp-ase activity of isolated but not granule-associated granzyme B. ATA, therefore, is not a specific endonuclease inhibitor and results obtained with ATA should be viewed cautiously.
 ...
PMID:Human granzyme B is essential for DNA fragmentation of susceptible target cells. 808 28

Caspase-3 initiates apoptotic DNA fragmentation by proteolytically inactivating DFF45 (DNA fragmentation factor-45)/ICAD (inhibitor of caspase-activated DNase), which releases active DFF40/CAD (caspase-activated DNase), the inhibitor's associated endonuclease. Here, we examined whether other apoptotic proteinases initiated DNA fragmentation via DFF45/ICAD inactivation. In a cell-free assay, caspases-3, -6, -7, -8, and granzyme B initiated benzoyloxycarbonyl-Asp-Glu-Val-Asp (DEVD) cleaving caspase activity, DFF45/ICAD inactivation, and DNA fragmentation, but calpain and cathepsin D failed to initiate these events. Strikingly, only the DEVD cleaving caspases, caspase-3 and caspase-7, inactivated DFF45/ICAD and promoted DNA fragmentation in an in vitro DFF40/CAD assay, suggesting that granzyme B, caspase-6, and caspase-8 promote DFF45/ICAD inactivation and DNA fragmentation indirectly by activating caspase-3 and/or caspase-7. In vitro, however, caspase-3 inactivated DFF45/ICAD and promoted DNA fragmentation more effectively than caspase-7 and endogenous levels of caspase-7 failed to inactivate DFF45/ICAD in caspase-3 null MCF7 cells and extracts. Together, these data suggest that caspase-3 is the primary inactivator of DFF45/ICAD and therefore the primary activator of apoptotic DNA fragmentation.
 ...
PMID:Caspase-3 is the primary activator of apoptotic DNA fragmentation via DNA fragmentation factor-45/inhibitor of caspase-activated DNase inactivation. 1052 51

Granzyme A (GzmA) activates a caspase-independent cell death pathway with morphological features of apoptosis. Single-stranded DNA damage is initiated when the endonuclease NM23-H1 becomes activated to nick DNA after granzyme A cleaves its inhibitor, SET. SET and NM23-H1 reside in an endoplasmic reticulum-associated complex (the SET complex) that translocates to the nucleus in response to superoxide generation by granzyme A. We now find the 3'-to-5' exonuclease TREX1, but not its close homolog TREX2, in the SET complex. TREX1 binds to SET and colocalizes and translocates with the SET complex. NM23-H1 and TREX1 work in concert to degrade DNA. Silencing NM23-H1 or TREX1 inhibits DNA damage and death of cells treated with perforin (PFN) and granzyme A, but not of cells treated with perforin and granzyme B (GzmB). After granzyme A activates NM23-H1 to make single-stranded nicks, TREX1 removes nucleotides from the nicked 3' end to reduce the possibility of repair by rejoining the nicked ends.
 ...
PMID:The exonuclease TREX1 is in the SET complex and acts in concert with NM23-H1 to degrade DNA during granzyme A-mediated cell death. 1681 37

The exact biological function of granzyme A, a granule-associated serine protease belonging to the tryptase family of proteases, is still a matter of debate because conflicting roles have been suggested, such as initiation of caspase-independent apoptosis-like cell death and endogenous modulation of inflammatory processes. In contrast to its well-studied family member, granzyme B, far less is known about the physiological targets of granzyme A. Using an N-terminal peptide-centric proteomics technology, the substrate specificity of human granzyme A was extensively characterized at the level of macromolecular protein substrates. Overall, more than 260 cleavage sites, almost exclusively favoring basic residues at the P1 position, in approximately 200 unique protein substrates, including the well-known in vitro substrates APEX-endonuclease 1 and different histones, were identified. Further substrate characterization was used to delineate physical properties in the substrate specificity profiles, which further highlights important aspects in protease/substrate biology.
 ...
PMID:The substrate specificity profile of human granzyme A. 2053 82

Granzyme B plays a key role in cell-mediated programmed cell death. We previously demonstrated that p53 is a functional determinant in the granzyme B-induced cytotoxic T-lymphocyte response. However, the pathways leading to activation of p53 by granzyme B remain incompletely understood. We now demonstrate that granzyme B-induced DNA damage signaling as revealed by histone H2AX phosphorylation and subsequent activation of the stress kinase CHK2. Confocal microscopy analysis indicates that granzyme B treatment of tumor cells induced an early translocation of endonuclease caspase-activated DNase. DNA microarray-based global transcriptional profiling and RT-PCR indeed revealed genes related to DNA damage. Among these genes, hSMG-1, a genotoxic stress-activated protein, was constantly upregulated in tumor cells following granzyme B treatment. Knockdown of the hSMG-1 gene in T1 tumor target cell line resulted in a significant inhibition of granzyme B- and CTL-induced killing. Our data suggest that granzyme B may exert cell death through DNA damage signaling and uncover a novel molecular link between the DNA damage pathway and granzyme B-induced cell death.
 ...
PMID:hSMG-1 is a granzyme B-associated stress-responsive protein kinase. 2130 99