Cop9 signalosome has multiple roles in the regulation of gcs-1p::gfp expression, arsenite resistance and longevity. csn-2, csn-4 and csn-5 RNAi significantly (A) reduce the basal and arsenite-induced intestinal expression of gcs-1p::gfp in prdx-2 mutant animals, (B) reduce the arsenite-induced expression of gcs-1p::gfp in wild-type animals, (C) increase the arsenite resistance but (D) reduce the lifespan of wild-type animals compared with animals maintained on empty vector control. In (A) and (B), levels of intestinal GFP were assessed under the fluorescent stereoscope using the scoring criteria illustrated in Figure 1 and described in Methods. Statistically significant differences between RNAi-treated samples and empty vector control are indicated. **P < 0.01; ***P< 0.001. (C) The survival on 7.5 mM arsenite and (D) lifespan of csn-2, csn-4 and csn-5 RNAi were statistically significant from empty-vector-control-treated animals (P < 0.001 in each case). Each experiment was repeated at least twice with similar results. GFP, green fluorescent protein; RNAi, RNA interference; WT, wild type.