COX4I1 and renal carcinoma: Interestingly, re-expression of pVHL in renal carcinoma cells increases the expression and activity of certain respiratory chain subunits including complex IV (CIV) subunits, mtCO-2 and COX IV (also known as COX4I1, COX4-1, and COX IV-1) [(18, 19), Supplementary Table 1], increases oxygen consumption rate (OCR) and mitochondrial DNA (mtDNA) content (20, 21).