The size of the topological domain modulates the B-Z transition of a (TG)n containing repeat.
Under negative superhelical stress, long (TG)n containing repeats experience a stepwise multiple B-Z transitions. We have investigated the effect of the plasmid size on this transitional behavior. A 66-bp (TG)n containing repeat from the 5'-untranscribed region of mouse ribosomal DNA was inserted in a 3-kb, a 6.5-kb and a 12.5-kb plasmids and its supercoil-driven B-Z transition was followed by OsO4 probing of topoisomer-populations. Our results show a clear correlation between the size of the topological domain and the extent of the region that converts cooperatively into Z-DNA at the initial transition.
Centre de Biophysique Moléculaire, C.N.R.S., Orléans, France.
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Albert
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M
Leng
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Rahmouni
D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000737:chemistry; D004275:DNA, Ribosomal / Q000737:chemistry* / Q000378:metabolism; D004278:DNA, Superhelical / Q000737:chemistry* / Q000378:metabolism; D006147:Guanine / Q000737:chemistry; D051379:Mice; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009690:Nucleic Acid Conformation; D010316:Particle Size; D010957:Plasmids / Q000737:chemistry*; D012091:Repetitive Sequences, Nucleic Acid; D013941:Thymine / Q000737:chemistry
D004275:DNA, Ribosomal; D004278:DNA, Superhelical; D006147:Guanine; D004247:DNA; D013941:Thymine