Formation of a Triple-Stranded DNA between d (GGA:TCC) Repeats and d(GGA) Repeat Oligonucleotides

抄録

Incubation of the 162-bp duplex containing d (GGA:TCC)₁₁ repeats with d (GGA)₁₁ and d (GGT)₁₁ oligonucleotides, but not with d(TCC)₁₁, gave a mobility-shifted band in polyacrylamide gel electrophoresis, suggestive of the triplex formation. The two conformers, however, showed difference in binding affinity and structure. The complex formed with d (GGT)₁₁ exhibited patterns protected from DNase I digestion and from modifications with osmium tetroxide and dimethyl sulfate. The patterns were conformed to a proposed triplex model. In contrast, the complex with d (GGA)₁₁ was sensitive to DNase I and to osmium tetroxide, which is reactive to pyrimidine bases of single-stranded DNA. These results suggest that the d(GGA:TCC)₁₁ and d(GGA)₁₁ triple-stranded complex forms a D-loop-like structure. By considering the ability of d(GGA)₁₁ oligonucleotides to form a parallel homoduplex, the structure may be one in which the GGA-strand of the duplex pairs with d (GGA)₁₁ in parallel, with the TCC-strand being looped out.