(A) Dis3L1 purified from HEK293T cells, (B) Exo9 subunits purified from E. coli, (C) assembled Exo9 and (D) assembled Exo10Dis3L1, analyzed by SDS-PAGE followed by fluorescent SYPRO staining. (E) Sequences of MLLFF-Stop mRNAs containing 7nt-, 27nt- and 47nt-long 3’UTRs, and the Mfold stem-loop in the 47nt-long 3’UTR. (F) Time courses of degradation of [ 32P]cap-27nt-3’UTR MLLFF-Stop mRNA by Dis3L1, Exo10Dis3L1 and Dis3L1 with Exo9 at 1.5 mM free [Mg2+]. Lane 1 contains RNA markers. Separation of lanes by white lines indicates that they were juxtaposed from the same gel. (G, H) The activities of Dis3L1 and Exo10Dis3L1 on (G) [32P]cap-7nt-3’UTR and (H) [ 32P]cap-47-nt-3’UTR MLLFF-Stop mRNAs after 30 min incubation at 1.5 mM free [Mg2+]. (I) [Mg2+]-dependence of the activity of Exo10Dis3L1 on [32P]cap-27nt-3’UTR MLLFF-Stop mRNA after 30 min incubation. Lane 6 contains RNA markers.