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. 2000 Apr 1;28(7):1535–1541. doi: 10.1093/nar/28.7.1535

Figure 4.

Figure 4

Interspersed d(AGG) triplets increase unwinding of G′2 tetraplex d(CGG)n by WRN helicase. The indicated G′2 tetraplex d(CGG)18 structures, with or without interspersed d(AGG) trinucleotides, were generated as in Figure 1 and 300 fmol aliquots of each G′2 DNA species were incubated at 37°C for 15 min under helicase assay conditions (see Materials and Methods). Electrophoretic resolution of tetraplex and single-stranded DNA and their quantification were conducted as in Figure 2. (A) Representative electrophoregrams of WRN-resolved G′2 tetraplex structures of tail d(CGG)18, tail d(A/CGG)18 1:7 and tail d(A/CGG)18 1:10. Migration of the single-stranded oligomers is viewed in control DNA samples that were heated at 100°C for 10 min to denature the tetraplex structures. (B) Titration of WRN activity of tetraplex DNA unwinding. Amounts of WRN-resolved G′2 DNA were quantified by phosphorimaging analysis. Zero amounts of unwound G′2 tetraplex DNA were determined in samples that were incubated at 37°C for 15 min without WRN.