Fig 1: MRPS31 suppression induces mitoribosomal dysfunction, OXPHOS defect, and cell invasiveness.MRPS31_high type cells (JHH4 and HepG2) were transfected with MRPS31 siRNA for 3 days. A Western blots. B Western blots after sucrose gradient sedimentation analysis of mitoribosome. MRPS29 (a small subunit protein) and MRPL13 and MRPL48 (large subunit proteins) were used as indicators of each subunit. Purple, blue and pink colored box indicated 55 S monosome, 39 S large subunit, and 28 S small subunit, respectively. C Mitochondrial translation activity. De novo synthesized proteins using L-homopropargylglycine (HPG)-conjugated Alexa Fluor 488 were detected by Western blot analysis. To distinguish cytosolic and mitochondrial translation activities, emetine (a cytosolic translation inhibitor) and chloramphenicol (CAP, a mitochondrial translation inhibitor) were used. The effect of MRPS31 knockdown on mitochondrial translation is shown in bottom panel. D Cellular OCR of JHH5 (left) and HepG2 (right) and their quantifications (basal and maximal rates, bottom). Nine independent experiments were performed. **p < 0.01 vs. siNC by student t test. E, F Cell invasion activity (left, N = 5) and cell growth (right, N = 3) of MRPS31-knockdowned JHH5 (E) and cell invasion activity (left, N = 3) and cell growth (right, N = 3) of MRPS31-knockdowned HepG2 (F). *p < 0.05 and **p < 0.01 vs. siNC.