Fig. 1

Mus81-Mms4 and MUS81-EME1 cleave fluorescein and streptavidin substrates. The nuclease activity assay for Mus81-Mms4 and MUS81-EME1 was performed by mixing the DNA substrate with the indicated protein complex concentrations and incubating for 15 min at 30 °C or 37 °C, respectively. The samples were resolved by native PAGE. The asterisk marks the position of fluorescein. Mus81-Mms4 and MUS81-EME1 efficiently cleave standard 3′ flap substrate (A), nicked duplex and 3′ flap substrates containing the fluorescein label at the 3′ end of the cleaved strand (B, C), and nicked duplex and 3′ flap with streptavidin (S) attached to the 3′ end of the cleaved strand (D, E). Numbers under the gel pictures represent the percentage of cleavage product calculated from the sum of substrate and product band intensities, except for the reaction with the streptavidin substrates, where the substrate band intensity of the control lane was taken as 100%. A small arrow (C) indicates Orange G containing the loading buffer used in that particular lane for gel migration control