(a) Data represent the mean±s.e.m. of the relative expression levels to GFP(OE) worms (n=4 independent experiments). Statistical comparisons were made by Student’s t test for unpaired samples. P value: **P<0.01, ****P<0.001. (b,c,d) Each lifespan graph shows a Kaplan–Meier survival plot of a single representative experiment. In each graph, experimental and control animals were grown in parallel. n=total number of uncensored animals/total number (uncensored+censored) of animals observed in each experiment. P values refer to experimental and control animals in a single lifespan experiment. See Supplementary Data 3 for statistical analysis, replicate data and independent OE lines results of lifespan experiments. (b) cct-8(OE) extends lifespan at 20 °C (log rank, P<0.0001). GFP(OE): median=14, n=73/96; cct-2, GFP(OE): median=14, n=65/96; cct-7, GFP(OE): median=13, n=46/74; cct-8, GFP(OE): median=16, n=70/96. (c) Both cct-8(OE) and cct-2(OE) worms live longer compared with control GFP(OE) strain at 25 °C (log rank, P<0.0001). cct-8(OE) worms live longer compared with cct-2(OE) and other cct(OE) strains (log rank, P<0.0001). GFP(OE): median=10, n=89/96; cct-2, GFP(OE): median=11, n=79/96; cct-5, GFP(OE): median=11, n=42/50; cct-7, GFP(OE): median=9, n=56/77; cct-8, GFP(OE): median=14, n=82/96. (d) Knockdown of cct-6 reduces the long lifespan induced by cct-8(OE) (log rank, P=0.0001). In contrast, loss of cct-6 does not decrease the lifespan of GFP(OE) worms. RNAi was initiated at day 1 of adulthood. GFP(OE) fed empty vector RNAi bacteria: median=10, n=74/96; GFP(OE) fed cct-6 RNAi bacteria: median=11, n=73/96; cct-8, GFP(OE) fed empty vector bacteria: median=13, n=77/96; cct-8, GFP(OE) fed cct-6 RNAi bacteria: median=12, n=79/96. (e) Native gel electrophoresis of GFP(OE) and cct-8,GFP(OE) worm extracts followed by immunoblotting with CCT-1 antibody (two different exposure times of the same membrane are shown). Overexpression of cct-8 induces an increase in the assembly of TRiC/CCT in the form of two stacked rings. *indicates a complex of ∼475 kDa which is strongly detected in worm lysates. The molecular weight suggests that this signal corresponds to single ring TRiC/CCT assembled forms. The images are representative of two independent experiments.