Fig. 1.

SILAC 1: identification of importin 13 cargoes using mass spectrometry. A, Experimental workflow. HZZ-tagged importin 13 or the HZZ-tag alone were immobilized on IgG-Sepharose and incubated with HeLa cell extracts containing either “light” (Lys0, Arg0), “medium” (Lys4, Arg6) or “heavy” (Lys8, Arg10) isotopes of lysine and arginine, with or without exogenous RanQ69L, as indicated. B, Scatter plot showing log2-ratios of importin 13 binding proteins enriched against the HZZ-affinity matrix in the presence (x axis) or absence (y axis) of RanQ69L. Colored proteins are either known importin 13 cargoes (underlined) or were further analyzed in this study. Gray squares correspond to proteins enriched with a log2 ratio ≥ 0.5. Gray crosses mark proteins that were considered insignificant. Red, proteins reduced by Ubc9 in SILAC 2–4. Blue, proteins enriched by RanQ69L in SILAC 2–4 (compare Fig. 2B, 2C). Proteins in dark colors were affected by overexpression of importin 13.