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)

Specific inhibitors of eukaryotic DNA topoisomerases I and II (camptothecin and VM-26, respectively) were used to examine the involvement of topoisomerases in DNA replication and chromatin assembly in vivo. When used singly, either camptothecin or VM-26 inhibited DNA synthesis in HeLa cells by more than 80%; when used simultaneously, the inhibitors effectively stopped replication, demonstrating that at least one class of topoisomerase must be active for fork propagation in vivo. To study nucleosome assembly during topoisomerase inhibition, three experimental strategies were employed: (1) pulse-chase experiments; (2) analyses of chromatin synthesized during residual replication in the presence of either camptothecin or VM-26; and (3) the assembly of previously replicated, unassembled DNA, generated in the presence of protein synthesis inhibitors. Using sensitivity to micrococcal nuclease and the maturation of non-nucleosomal replication intermediates as criteria, neither camptothecin nor VM-26, alone or in concert, inhibited nucleosome assembly under any experimental protocol tested. These data provide evidence that, although topoisomerase activity is essential for DNA replication, neither continuous fork propagation nor topoisomerase activity is required for chromatin assembly on new DNA.
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PMID:Inhibitors of topoisomerases I and II arrest DNA replication, but do not prevent nucleosome assembly in vivo. 255 22

HeLa cell nuclei with DNA labeled with [3H] thymidine have been preincubated under varying conditions and then incubated with micrococcal nuclease. Aliquots, removed at increasing times, were analyzed for mononucleosomal size DNA and for acid-soluble DNA, the ratios were plotted and a slope was determined. Preincubation with ATP and a regenerating system increased the slope 2 fold. Optimum ATP concentrations were above 0.25 mM. The ATP effect was reversed by novobiocin. No inhibition of the ATP effect was observed with nalidixic acid, coumermycin, oxolinic acid, VM-26, aphidicolin, or 3 amino-benzamide. NAD or cAMP or cGMP had no effect with or without ATP. Other nucleoside triphosphates could substitute to varying degrees for ATP as could ATP analogues. Nuclei from log phase cells showed no ATP effect, but log phase cells, partially depleted of ATP by incubation with deoxyglucose, showed the effect. The effect was lost in nuclei on long-term storage. No evidence was found for differential degradation of core histones, histone H-1 or DNA, and there was no evidence of nucleosome sliding.
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PMID:The effect of preincubation of HeLa cell nuclei with ATP on the degradation of mononucleosomal DNA by micrococcal nuclease. 301 48