Positional enhancer-blocking activity of the chicken beta-globin insulator in transiently transfected cells.
It is thought that insulators demarcate transcriptionally and structurally independent chromatin domains. Insulators are detected by their ability to block enhancer-promoter interactions in a directional manner, and protect a transgene from position effects. Most studies are performed in stably transformed cells or organisms. Here we analyze the enhancer-blocking activity of the chicken beta-globin insulator in transient transfection experiments in both erythroid and nonerythroid cell lines. We show that four tandem copies of a 90-bp fragment of this insulator were able to block an enhancer in these experiments. In circular plasmids, placement on either side of the enhancer reduced activity, but when the plasmid was linearized, the enhancer-blocking activity was observed only when the insulator was placed between the promoter and the enhancer. These observations are consistent with the position-dependent enhancer-blocking activity of the insulator observed in stable transformation experiments.
Recillas-Targa
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Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA. frecilla@ifisiol.uman.mx
Bell
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Felsenfeld
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D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002645:Chickens; D004742:Enhancer Elements, Genetic; D004912:Erythrocytes / Q000378:metabolism; D005914:Globins / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D010957:Plasmids; D011401:Promoter Regions, Genetic; D014162:Transfection
D005914:Globins