(A) let-70 gene structure and mutations/RNAi clones used in our studies. Black boxes, exons; white boxes, 5’ or 3’ untranslated regions. Scale bar, 200 bp. (B) Combined DIC and fluorescent images of let-70(RNAi) adult male. lag-2p::GFP marks the linker cell. Arrow, linker cell. White line, cloaca. Scale bar, 10 μm. (C) EM of surviving let-70(RNAi) linker cell. Scale bar, 2 μm. Asterisk, mitochondria, Arrowhead, ER, N, nucleus, nl, nucleolus. (D) Purified 6xHis-LET-70, Drosophila UBA1, DIAP1 and ubiquitin. causes DIAP1 auto-ubiquitination. (E-H) Linker cell survival in indicated genotypes. No. animals scored, inside bars. Error bars, SEM. *p<0.001; **p<0.0001; Fisher’s Exact Test; ns, not significant. Animals contained qIs56 and him-5(e1490). In (F) animals also contained rrf-3(pk1426) for increased RNAi efficiency. In LC-only experiments, mig-24p was used to drive rde-1 cDNA in rde-1(ne219); him-8(e1489); qIs56 mutants. ND, not determined.