Figure 7

A conserved ER membrane complex discovered in yeast promotes CFTR-ΔF biogenesis. (A) Six of seven members of the recently described ER membrane complex (EMC) fell into two clusters (EMC genes are labeled in red; 'EMC1 o/l' indicates YCL046w, which overlaps EMC1/YCL045c). Columns represent different gene-drug interactions as described in methods. (B) The interaction plots for EMC genes (corresponding to genes in panel A) suggested the complex has a pro-biogenesis effect specific for Yor1-ΔF. The similarity in profiles is consistent with the hypothesis that each EMC gene is required for the function of the complex in promoting Yor1-ΔF biogenesis. (C) By pulse chase analysis, deletion of SOP4 did not affect the half-life of Yor1-ΔF670. Quantification of three independent experiments is shown; error bars represent standard deviation. (D) Yor1-ΔF670 synthesis was reduced in the sop4-Δ0 strain based on the total amount of ³⁵S-Met/Cys incorporated during the initial 10-min pulse. Three independent experiments were quantified; error bars represent standard deviation. Wild-type Yor1 and the GPI-anchored protein, Gas1, were unaffected by SOP4 deletion. (E) TTC35, the human homolog of EMC2, is required for normal biogenesis of CFTR-ΔF. HeLa cells, transiently expressing CFTR-ΔF at 27°C, were co-transfected with control siRNA, 10 nM TTC35 siRNA, or 25 nM TTC35 siRNA as indicated. Protein levels of TTC35, CFTR-ΔF, and α-tubulin were monitored from whole cell lysates by western blot, and (at right) relative abundance from three independent experiments was quantified by densitometry; error bars represent standard deviation, significance was assessed by a paired two-tailed t-test.