Figure 1.

MutSβ promotes (CAG)_n or (CTG)_n hairpin retention synthesis in HeLa nuclear extracts. (A) Diagram of hairpin removal/retention assay by Southern blot analysis. The purple bar shows the ³²P-labeled oligonucleotide probe, which specifically anneals to the newly synthesized strand near the BsrBI site. The complete primer sequence of a CTG hairpin substrate used in this study is also shown. (B) Southern blot analysis showing the effect of MutSβ on (CAG)₅ or (CTG)₅ hairpin retention/removal during DNA synthesis in HeLa nuclear extracts. DNA hairpin substrate (0.15 pmol) was incubated with limited amount (30 μg) of HeLa nuclear extracts in the presence of increasing amounts of purified MutSβ. The resulting products were examined by Southern blot analysis. (C, D) Quantification of hairpin-retained products and hairpin-removed products shown in B, respectively. The data were from three independent experiments and the error bar represents SD.