RIP140 directly interacts with LSD1 to regulate its activity. (A): Pull-down assay for HA-LSD1 full-length (FL) interaction with Flag-RIP140 (FL), Flag-RD1, Flag-RD1-2, Flag-RD2-3, or Flag-RD3-4. Positive interaction denoted by *. (B): Pull-down assay for Flag-RIP140 (FL) interaction with HA-LSD1 (FL) or LSD1 truncated proteins. Positive interaction denoted by *. (C): In vitro LSD1 demethylase activity detected using free bulk histones as substrates and bacteria-expressed LSD1 and RIP140 (lower panel), analyzed by Western blotting using anti-H3k4me2 (upper) or anti-H3k4me1 (middle). Controls include antibody detected H3 (H3 panel).