Figure 1: Mild overexpression of miR-17-19b in B cell lymphoma triggers a global proteomic response.

(a) Expression levels of MYC (left panel) and the mature forms of miR-17-19b components (right panel) were profiled in Epstein–Barr virus (EBV) positive (Daudi and Raji) and EBV negative (CA46 and Ramos) human Burkitt lymphoma cell lines, as well as in primary lymphomas and pre-tumoral (PT) B cells isolated from λ-MYC transgenic mice. Wild-type mouse splenic B cells were used as controls. (b) Scheme of the SILAC experiment. Control and miR-17-19b overexpressing cells (miR cells) were cultured in light (L) and heavy (H) media, respectively. Labelled cells were combined in 1:1 ratio and analysed by liquid chromatography–tandem mass spectrometry. In parallel, from the same samples, total RNA was prepared and analysed by microarray. Data were subjected to statistical and functional analysis. Intensity peak ratios between heavy and light peptides (H/L ratio) reflect changes in protein expression. (c) Reproducibility of the SILAC proteome in the two experimental data sets, #2567-1 and #2567-2 (d) Log₂-transformed H/L protein ratio distributions of the two functional experiments (miR cells versus control for #2567-1 in red and #2567-2 in blue) and of the control experiment (control cells versus control cells, in black) indicate a strong proteome response upon induction of the cluster, with both, up- and downregulated proteins. (e) The comparison of log₂ fold changes at protein and mRNA levels shows low correlation (r=0.51), with significantly larger protein dispersion. (See related Supplementary Figs 1 and 2).