Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.24.3 (collagenase)
 18,340 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The procarcinogen, 2-acetylaminofluorene, the direct-acting carcinogen, methyl methanesulfonate, and two other hepatocarcinogens, thioacetamide and urethan, were tested for their ability to elicit unscheduled DNA synthesis in adult rat hepatocytes maintained in primary culture on collagen gel-nylon mesh. The carcinogens, dissolved in dimethyl sulfoxide were added to 6-hr or to 28-hr cultures along with [methyl-3H]thymidine (1 muCi/ml medium) in the presence of 10 mM hydroxyurea. Twelve hr later, the hepatocytes were harvested from the cultures with collagenase, and their DNA was purified on CsCl isopyknic gradients. Unscheduled DNA synthesis was measured as the increase in [methyl-3H]thymidine radioactivity incorporated per microgram DNA of the carcinogen-treated cultures as compared with that of control cultures. Both 2-acetylaminofluorene and methyl methanesulfonate demonstrated a concentration-dependent stimulation of unscheduled DNA synthesis in the 6-hr hepatocyte cultures. However, the response of the 28-hr cultures to these two carcinogens was absent unless the hepatocytes were preincubated for 22 hr in culture medium supplemented with 10(-5) M dexamethasone and 10(-6) M glucagon or in a more complete hormone-supplemented medium. Thioacetamide and urethan, on the other hand, failed to elicit a concentration-dependent unscheduled DNA synthesis under these conditions. The results obtained with this culture system are similar to those of other short-term tests for chemical carcinogenicity and support the potential use of the collagen gel-nylon mesh-hepatocyte primary culture as an in vitro screen for chemical carcinogens. Furthermore, this study suggests the importance of specific hormones in maintaining the capability for repair of DNA damage produced by carcinogenic and mutagenic chemicals in cultured hepatocytes.
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PMID:Use of primary cultures of adult rat hepatocytes on collagen gel-nylon mesh to evaluate carcinogen-induced unscheduled DNA synthesis. 700 Mar 42

The present report demonstrates differential DNA-repair activity among 14 strains of immature (20 +/- 2 days old) male mice (inbred strains: C57BL/6J, RF/J, Nude homo/nu, RIII/2J, PL/J, AKR/J, Nude hetero/nude, C3H/HeJ, SWR/J, SM/J, ST/J, LP/J, BALB/cJ and random-bred strain: CD-1). The prespermiogenic cells were isolated and enriched by collagenase-trypsin digestion of seminiferous tubules and subsequent 3% albumin-gradient centrifugation. Enriched prespermiogenic cells demonstrated a viability greater than 95% by trypan blue exclusion criteria. For in vitro unscheduled DNA synthesis (UDS) determination, prespermiogenic cells (10(6) cells/ml) were incubated with methyl methanesulfonate (0.4 mM) in the presence of 20 mM hydroxyurea (HU). At 20 mM HU concentration, 90% of S-phase DNA activity in prespermiogenic cells was inhibited and thus, the net UDS activity following MMS exposure was readily determined. MMS-induced UDS activity in the CD-1 mouse strain was both linear up to 4 h of incubation and dose-dependent at 4 h of incubation. The apparent Km for MMS-induced UDS activity in prespermiogenic cells was approx. 1.8 x 10(-4) M. Of the 14 mice strains tested, C57BL/6J and RF/J exhibited the highest DNA-repair activity, while BALB/cJ, LP/J, and ST/J showed the lowest. A maximal difference in UDS activity of 3.5-fold was observed between C57BL/6J and BALB/cJ. Furthermore, a 2.5-fold difference was also noted between RF/J and LP/J mouse strains. Thus, wide variations in DNA-repair activity among 14 mouse strains were clearly demonstrated. Whether genetically select mouse strains with the lowest DNA-repair activity should have greater sensitivity toward environmental mutagens needs to be tested.
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PMID:Differential DNA-repair activity in prespermiogenic cells of various mouse strains. 720 82

Transcriptional activation of c-fos in response to both serum stimulation and DNA damage requires the serum response element. The inability of in vitro aged or senescent fibroblasts to proliferate in response to serum has been shown to be associated with repressed c-fos expression and reduced AP-1 binding activity. In contrast, we have observed similar levels of c-fos mRNA and protein expression in young (early passage) and old (late passage) cells following their treatment with ultraviolet (UV) irradiation or methyl methanesulfonate (MMS). Thus, the early events in the signal transduction pathway leading to transcriptional activation of c-fos following DNA damage are distinct from those mediating the gene's expression in response to mitogenic stimulation. Despite normal levels of c-fos expression, we observed a reduced level of AP-1 binding activity in old cells relative to young cells treated with UV irradiation or MMS. Reduced AP-1 binding activity is associated with reduced expression of the AP-1-dependent gene, collagenase, in old cells treated with DNA damaging agents. Since other DNA damage-inducible genes also contain an AP-1 regulatory element presumed to play a role in their expression, reduced AP-1 binding activity is likely to have a major impact on the old cell's ability to respond appropriately to DNA damage.
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PMID:Alterations in the molecular response to DNA damage during cellular aging of cultured fibroblasts: reduced AP-1 activation and collagenase gene expression. 779 Mar 98

Treatment of cells with agents that damage DNA leads to the induction of numerous genes. Recent studies aimed at understanding the events preceding the transcriptional activation of some of these DNA damage-inducible genes in mammalian cells have demonstrated that various extranuclear protein kinases are involved in the signaling cascades. The mammalian GADD153 gene, a member of the CCAAT enhancer-binding protein family of transcription factors, is highly induced by a variety of DNA-damaging agents as well as by certain growth arrest conditions and oxidative stresses. We have examined the effects of numerous protein kinase and phosphatase inhibitors on the DNA damage-induced expression of GADD153, to identify the signal transduction components involved in its transcriptional regulation. In contrast to the transcriptional activation of c-jun and collagenase in response to DNA damage, GADD153 induction involves neither protein kinase C nor tyrosine kinases but does appear to require an unidentified serine-threonine-kinase. Elevation of intracellular glutathione levels by treatment with N-acetylcysteine did not affect the methyl methanesulfonate-induced expression of the GADD153 gene, although it did diminish cadmium chloride-induced expression. These findings suggest that oxidative stress and DNA damage regulate GADD153 transcription through different pathways. Based on our findings and those of others with respect to other DNA damage-inducible genes, we propose a model depicting the complex pathways which appear to be involved in the regulation of mammalian genes in response to genotoxic stress and in which the DNA damage-induced expression of GADD153 represents a unique pathway independent of either protein kinase C or tyrosine kinase.
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PMID:The pathway regulating GADD153 induction in response to DNA damage is independent of protein kinase C and tyrosine kinases. 813 9

Activation of c-Jun N-terminal kinases (JNKs)/stress-activated protein kinases is an early response of cells upon exposure to DNA-damaging agents. JNK-mediated phosphorylation of c-Jun is currently understood to stimulate the transactivating potency of AP-1 (e.g., c-Jun/c-Fos; c-Jun/ATF-2), thereby increasing the expression of AP-1 target genes. Here we show that stimulation of JNK1 activity is not a general early response of cells exposed to genotoxic agents. Treatment of NIH 3T3 cells with UV light (UV-C) as well as with methyl methanesulfonate (MMS) caused activation of JNK1 and an increase in c-Jun protein and AP-1 binding activity, whereas antineoplastic drugs such as mafosfamide, mitomycin C, N-hydroxyethyl-N-chloroethylnitrosourea, and treosulfan did not elicit this response. The phosphatidylinositol 3-kinase inhibitor wortmannin specifically blocked the UV-stimulated activation of JNK1 but did not affect UV-driven activation of extracellular regulated kinase 2 (ERK2). To investigate the significance of JNK1 for transactivation of c-jun, we analyzed the effect of UV irradiation on c-jun expression under conditions of wortmannin-mediated inhibition of UV-induced stimulation of JNK1. Neither the UV-induced increase in c-jun mRNA, c-Jun protein, and AP-1 binding nor the activation of the collagenase and c-jun promoters was affected by wortmannin. In contrast, the mitogen-activated protein kinase/ERK kinase inhibitor PD98056, which blocked ERK2 but not JNK1 activation by UV irradiation, impaired UV-driven c-Jun protein induction and AP-1 binding. Based on the data, we suggest that JNK1 stimulation is not essential for transactivation of c-jun after UV exposure, whereas activation of ERK2 is required for UV-induced signaling leading to elevated c-jun expression.
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PMID:Activation of c-Jun N-terminal kinase 1 by UV irradiation is inhibited by wortmannin without affecting c-iun expression. 1002 64