Fig. 1: US9 contains a slowly cleaved SP.

a RKO MICA*008-HA cells co-expressing an empty vector (EV) or US9 attached to a C-terminal 6XHis tag were lysed. Lysates were mock-treated (−) or digested with endoglycosidase H (endoH; +) and then blotted. Anti-His tag was used to visualize protein expression, with anti-vinculin as loading control. Representative of at least three independent experiments. b RKO MICA*008-HA cells expressing EV or US9 were radioactively labeled for 20 min (pulse) and then chased in the absence (−) or presence (+) of 10 µM MG132. Digitonin-lysates were prepared at the indicated chase times (in minutes). An anti-His tag immunoprecipitation was performed. All samples were digested with endoH. Representative of three independent experiments. Ladder was visualized at a higher contrast, shown in Fig. S1b. c Quantification of the US9 isoforms shown in (b). AU arbitrary units. d Graphic representation of US9 protein sequence coverage detected by mass spectrometry analysis of the two US9 isoforms: SP⁺ and SP⁻. Sequence coverage % and US9 domains are indicated. See also Supplementary Data 1–2, figure S1 and the Source Data file for experimental data.