caa a22 4500 46582045X CHVBK 20180323112134.0 cr unu---uuuuu 170327e19900501xx s 000 0 eng 10.1007/BF01233361 doi (NATIONALLICENCE)springer-10.1007/BF01233361 Chromosome aberration induction in Chinese hamster ovary cells by restriction enzymes with different methylation sensitivity [Elektronische Daten] [Richard Winegar, John Phillips, Louise Lutze, William Morgan] The isoschizomer pair MspI and HpaII were used to investigate whether the putative specificity of restriction endonucleases would be maintained when they were introduced into mammalian cells. Although both enzymes recognize the sequence CCGG, HpaII will cut only if the internal cytosine is unmethylated, whereas MspI will cut regardless of the methylation status. Cleavage results in a cohesive-end DNA double-strand break, which can lead to the formation of chromosome aberrations. Since mammalian DNA is heavily methylated, one would expect MspI to be much more effective than HpaII at inducing chromosome aberrations in Chinese hamster ovary cells. In fact, during G1, MspI induced a >90-fold higher number of aberrations than did HpaII. Cell cycle studies indicated that during early S there was a 30-fold increase in HpaII-induced aberrations. This increase may be due to increased accessibility of replicating hypomethylated DNA. Cells that were treated with the demethylating agent 5-aza-2′-deoxycytidine (AzdC) displayed only a moderate increase in HpaII-induced aberrations during G1. This observation, together with the results of restriction enzyme analysis of genomic DNA, indicated that demethylation was incomplete. The effects of AzdC on the induction of aberrations by MspI suggested that AzdC increases chromatin accessibility. Our results were consistent with the expected specificity of MspI and HpaII. Thus, it appears that restriction endonucleases can play a useful role in determining the biological consequences of DNA double-strand breaks. Plenum Publishing Corporation, 1990 Winegar Richard Laboratory of Radiobiology and Environmental Health, University of California, 94143-0750, San Francisco, California aut Phillips John Laboratory of Radiobiology and Environmental Health, University of California, 94143-0750, San Francisco, California aut Lutze Louise Laboratory of Radiobiology and Environmental Health, University of California, 94143-0750, San Francisco, California aut Morgan William Laboratory of Radiobiology and Environmental Health, University of California, 94143-0750, San Francisco, California aut Somatic Cell and Molecular Genetics Kluwer Academic Publishers-Plenum Publishers 16/3(1990-05-01), 251-256 0740-7750 16:3<251 1990 16 11188 https://doi.org/10.1007/BF01233361 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF01233361 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Winegar Richard Laboratory of Radiobiology and Environmental Health, University of California, 94143-0750, San Francisco, California aut NATIONALLICENCE 700 1- Phillips John Laboratory of Radiobiology and Environmental Health, University of California, 94143-0750, San Francisco, California aut NATIONALLICENCE 700 1- Lutze Louise Laboratory of Radiobiology and Environmental Health, University of California, 94143-0750, San Francisco, California aut NATIONALLICENCE 700 1- Morgan William Laboratory of Radiobiology and Environmental Health, University of California, 94143-0750, San Francisco, California aut NATIONALLICENCE 773 0- Somatic Cell and Molecular Genetics Kluwer Academic Publishers-Plenum Publishers 16/3(1990-05-01), 251-256 0740-7750 16:3<251 1990 16 11188 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer