Endogenous miR-93 and miR-155 restrain AID protein expression. (A) Diagram of miR sponge expression vector. TS indicates an AID 3'UTR miR target site detailed in 1A. The miR-93 sponge produces a polyadenylated concatamer of 11 individual 93 TSs. Analogously designed, the miR-155 sponge contains 10 individual miR-155 TSs, and the ctl sponge contains 14 individual shLacZ targets. CMVp, immediate early cytomegalovirus promoter; SV40pA, simian virus 40 polyadenylation signal. (B) Representative western demonstrating that transient transfection of MCF-7 cells with the miR-93 or miR-155 sponges results in dose responsive increases in AID protein levels as compared to control. Ctl, shLacZ target site sponge transfected; PCNA, Proliferating Cell Nuclear Antigen. (C) Relative AID mRNA levels corresponding to replicate transfections performed as in B (n = 3) as determined by quantitative PCR.