(a) The expression of several cct subunits decreases with age. In contrast, we did not find significant differences in cct-1 and enpl-1, the C. elegans orthologue to the human chaperone HSP90B1. Data represent the mean±s.e.m. of the relative expression levels to day 1 adult worms grown at 20 °C (n=4 independent experiments). These experiments were performed with the sterile control strain fer-15(b26)II;fem-1(hc17). (b) When subjected to heat stress (34 °C) at day 1 of adulthood, both cct-8(OE) and cct-2(OE) worms show similar survival rates compared with the control strain (GFP(OE): median=11, n=70/72; cct-2, GFP(OE): median=10, n=71/72; cct-8, GFP(OE): median=9, n=70/72). (c) In contrast, cct-8(OE) (log rank, P<0.0001) and cct-2(OE) (log rank, P=0.0036) worms survive longer than control strain when subjected to heat stress at day 5 of adulthood (GFP(OE): median=14, n=57/58; cct-2, GFP(OE): median=16, n=57/57; cct-8, GFP(OE): median=17, n=57/57). (d) hsf-1-RNAi-treated cct(OE) worms were long-lived compared with control strain under the same treatment (log rank, P<0.0001). RNAi was initiated at day 1 of adulthood. GFP(OE) fed hsf-1 RNAi bacteria: median=7, n=90/96; cct-2, GFP(OE) fed hsf-1 RNAi bacteria: median=8, n=82/96; cct-8, GFP(OE) fed hsf-1 RNAi bacteria: median=9, n=72/96. (e) Ectopic expression of cct-8 and cct-2 improve motility in polyQ67 worms grown at 25 °C. In the left panel, each point represents the average thrashing rate of a single 3 day-adult animal over a period of 30 s. In the right panel, bar graphs represent average±s.e.m. of these data (GFP(OE);Q67 (n=37), cct-2,GFP(OE);Q67 (n=38), cct-8,GFP(OE);Q67 (n=38)). All the statistical comparisons were made by Student’s t test for unpaired samples. P value: ***P<0.001, ****P<0.0001. (f) Filter trap indicates that cct-8 OE results in decreased polyQ aggregates (detected by anti-GFP antibody). Right panel: SDS–PAGE analysis with antibodies to GFP and α-tubulin loading control. The images are representative of two independent experiments. See Supplementary Data 3 for statistical analysis and replicate data of lifespan and stress assays experiments.