(C) The autophagy activity is significantly increased in cells with the UBE4B and LSD1 double knockdown. The in vivo activity of the ATG4B protease, which cleaves LC3 precursors, was quantified via a Gaussia luciferase release assay (see S5D Fig., S5E Fig., and Materials and Methods for details). The HCT116 cells were analyzed 48 h after the initiation of the knockdown. 