H-DNA and Z-DNA in the mouse c-Ki-ras promoter.
The mouse c-Ki-ras protooncogene promoter contains a homopurine-homopyrimidine domain that exhibits S1 nuclease sensitivity in vitro. We have studied the structure of this DNA region in a supercoiled state using a number of chemical probes for non-B DNA conformations including diethyl pyrocarbonate, osmium tetroxide, chloroacetaldehyde, and dimethyl sulfate. The results demonstrate that two types of unusual DNA structures formed under different environmental conditions. A 27-bp homopurine-homopyrimidine mirror repeat adopts a triple-helical H-DNA conformation under mildly acidic conditions. This H-DNA seems to account for the S1 hypersensitivity of the promoter in vitro, since the observed pattern of S1 hypersensitivity at a single base level fits well with the H-DNA formation. Under conditions of neutral pH we have detected Z-DNA created by a (CG)5-stretch, located adjacent to the homopurine-homopyrimidine mirror repeat. The ability of the promoter DNA segment to form non-B structures has implications for models of gene regulation.
Pestov
D G
DG
Department of Genetics, University of Illinois, Chicago 60612.
Dayn
A
A
Siyanova EYu
George
D L
DL
Mirkin
S M
SM
D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000737:chemistry* / Q000235:genetics; D004278:DNA, Superhelical / Q000737:chemistry; D051379:Mice; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics*
D004278:DNA, Superhelical; D004247:DNA; D016283:Proto-Oncogene Proteins p21(ras)