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Albert, AC ; Roman, AM ; Bouche, G ; Leng, M ; Rahmouni, AR

Gradual and oriented b-z transition in 5’-untranscribed region of mouse ribosomal DNA

Journal of Biological Chemistry 269 (30) 19238-19244

par Administrateur - publié le

Abstract :

The structural transition of an alternating purine-pyrimidine sequence ((CG)(5)(TG)(28)) from the 5’-untranscribed region of the mouse ribosomal DNA was analyzed by two-dimensional gel electrophoresis and chemical probes. The repeat undergoes a supercoil dependent gradual and oriented B-Z transition. At a threshold level of negative supercoiling, a limited region of the repeat encompassing the (CG)(5) motif converts cooperatively into Z-DNA. As the superhelical stress increases, the Z-structure propagates along the remaining part of the repeat by successive transitions until the full-length sequence is converted. By in situ OsO4 probing experiments, we show also that this (TG)(n)-containing repeat adopts the Z-structure in Escherichia coli.