Antibody Validation and siRNA Screening

Antibodies to human Sec61β (1:10,000 dilution), TRAPα (ref. ^{49 (link)}; 1:5,000) and TMCO1 (ref. ^{9 (link)}; 1:5,000) were described previously. Other antibodies were obtained from the following commercial sources: rabbit anti-nicalin (A305-623A-M; 1:1,000) and rabbit anti-CCDC47 (A305-100A; 1:2,000) from Bethyl Laboratories; mouse anti-HA (326700; 1:1,000), goat anti-NOMO (PA5-47534; 1:1,000), rabbit anti-TMEM147 (PA5-95876; 1:1,000), rabbit anti-Asterix (PA5-66788; 1:5,000), rabbit anti-C20Orf24 (PA5-43332; 1:1,000) and rabbit anti-Sec61α (PA5-21773; 1:1,000) from Invitrogen; rabbit anti-uL22 from Abgent (AP9892b; 1:1,000); mouse anti-tubulin (ab11304; 1:1,000) and mouse anti-HRP (ab6728; 1:1,000) from Abcam; mouse anti-Flag (F1804; 1:1,000), rabbit anti-Flag (F7425; 1:1,000), rabbit anti-peroxidase (SAB3700863; 1:10,000) and goat anti-peroxidase (A5420; 1:20,000) from Sigma; mouse anti-STT3A (H00003703-M02; 1:1,000) from Novus Biologicals; mouse anti-BiP/GRP78 (610979; 1:1,000) from BD Biosciences. siRNAs were purchased from Thermo Fisher: negative control (4390843), TMCO1 (s29085), C20Orf24 (s31821), Asterix (s28089), CCDC47 (s32576), Nicalin (s32411) and TMEM147 (s20404).