title: Transcription of the human beta-globin gene is stimulated by an SV40 enhancer to which it is physically linked but topologically uncoupled.
abstract: One postulated mechanism for how the SV40 enhancer stimulates transcription of linked genes involves the enhancer as a binding site for a sequence-specific "gyrase" activity. We sought to test this hypothesis directly by constructing a novel heteroduplex circle, termed a tailed-circle, in which one of the strands contains an extra palindromic sequence base-paired into a hairpin structure. The human beta-globin gene is placed in the circle and the SV40 enhancer on the hairpin tail, where a bound topoisomerase cannot supercoil the circle. Upon transfection of this DNA into HeLa cells the SV40 enhancer on the hairpin arm is still able to stimulate transcription of the beta-globin gene. Southern blot analysis of the DNA after transfection does not demonstrate any repair or replication of the tailed-circle in vivo. These results argue against the sequence-specific gyrase model for SV40 enhancer action.
mesh_terms: D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D004274:DNA, Recombinant / Q000378:metabolism; D004278:DNA, Superhelical / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D005809:Genes, Regulator; D005813:Genes, Synthetic; D005914:Globins / Q000096:biosynthesis* / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D009690:Nucleic Acid Conformation; D010957:Plasmids; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D013539:Simian virus 40 / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D004274:DNA, Recombinant; D004278:DNA, Superhelical; D011994:Recombinant Proteins; D005914:Globins; D004250:DNA Topoisomerases, Type II