Fig. 2. SENP5 is broadly distributed and deSUMOylates multiple mitochondrial substrates. (A) COS-7 cells transfected with SENP5:YFP were fixed; YFP fluorescence indicates that SENP5 localizes mainly in nucleolus with clear cytosolic and nuclear staining (bar, 10 µm). (B) COS-7 cells were harvested and fractionated to obtain mitochondria and cytosol. In addition to the total extracts, 50 µg of each fraction were loaded in a gel to examine endogenous SENP5 distribution. Markers of different fractions (HSP70 for cytosol, HSP60 and Tom20 for mitochondria) are indicated. (C) Untransfected COS-7 cells or those expressing SENP5:YFP were harvested and mitochondria were isolated. Of total cell lysate (Tot) or mitochondriaenriched fractions (Mit) 100 µg were separated by SDS-PAGE to examine the endogenous mitochondrial SUMO1 conjugates. Shown are short and long exposures of the anti-SUMO1 western blots (top and middle panel), together with anti-DRP1 and anti-Tom20 detection (bottom panel). SUMO1 conjugates in the mitochondrial fraction are indicated by circles, arrows indicate DRP1 high molecular mass conjugates. UTF, untreated cell fraction.