Figure 3. Lifespan shortening is due to expression of mature miR-277. (A) The sequence and secondary structure of wild-type and mutant pre-miR-277 hairpins; the sequence of mature miR-277 is depicted in green and the the cleavage sites for Drosha and Dcr-1 are indicated by a dashed red line. (B) Expression of mature miR-277 from wild-type and mutant pre-miR-277 hairpins; left panel, the constructs were transiently transfected into S2 cells right panel, RNA was extracted from the abdomen of transgenic flies and miR-277 levels were compared with wild-type flies. (C) Constitutive expression of wild-type pre-miR-277 as well as the perfect dsRNA hairpin (mut. 2) results in lifespan shortening compared with constitutive expression of the hairpin with additional bulges (mut. 1). The transgenic lines used for these experiments were established in a w¹¹¹⁸ background but not backcrossed into yw (as in Fig. 2), food type was HSHP.