G3BP1 depletion decreases cell proliferation. Breast cancer cell lines MCF-7 (A, E, F), MDA-MB-231 (B), MDA-MB-468 (C) and BT549 (D) cells were transiently transfected with 40 nM siRNA targeting G3BP1 and/or G3BP2 for 72 hours prior to [3H]-thymidine incubation for 6 hours. Number of MCF-7 (G) and MDA-MB-468 (H) cells was analyzed after transfection with siRNA targeting G3BP1 and/or G3BP2 for 96 hours by counting viable cells, identified by trypan blue exclusion. Data (mean ± SEM, n = 3) are expressed as [3H]-thymidine incorporation (A-F) and as total number of viable cells (G-H) related to control cells. * < 0.05, ** < 0.01, *** < 0.001 according to ANOVA followed by Duncan’s multiple range test. Western blots demonstrate downregulation of G3BPs by their cognate siRNAs (I-K).