Transcriptional repression requires the recruitment of multiprotein complexes assembled on central scaffolding proteins referred to as co-repressors. We used siRNAs against various candidate corepressors in the iNOS-luciferase reporter assay and identified CoREST as being essential for Nurr1-mediated repression (Fig. 4A and Fig. S8A). CoREST has been considered to be dedicated to repression of neuronal genes in non-neuronal cells or early precursors by binding to neuron-restrictive silencer factor (NRSF)/RE1-silencing transcription factor (REST) (Ballas et al., 2005). CoREST assembles many chromatin-modifying enzymes, including histone methyltransferase G9a, histone demethylase, lysine-specific demethylase (LSD1) and histone deacetylase (HDAC) 1 and 2 (Shi et al., 2003). Using Nurr1-mediated repression of iNOS-luciferase as an assay, we observed that G9a, LSD1 and HDAC1 were also required for Nurr1-CoREST-mediated repression (Fig. S8B). Using co-IP, we also found that LPS stimulated interaction of Nurr1 and CoREST in BV2 cells (Fig. 4B and Fig. S8C). Although the CoREST complex consists of many proteins, the interaction between Nurr1 and CoREST seemed to be direct, as indicated by in vitro GST-pull down assay (Fig. S8D). This interaction was mediated by the DNA-binding domain
