Figure 5: AR-interacting proteins are WINAC complex components and transcriptional activators of VDR-mediated gene expression. Presented is a simplified version of the BIOCARTA pathway “control of gene expression by Vitamin D receptor (VDR)” illustrating how AR and VDR may compete for shared coregulators. (a) In AR copurifications from proliferating P17 cells (33°C), the transcriptional activators EP300, SRC1*, and 5 proteins from the ATP, dependent chromatin remodelling complex WINAC: SMARCA4, ARID1A, ARID1B, SMARCC1, and SMARCD1 were identified. Under proliferating conditions, AR would therefore compete with VDR for 5 WINAC components and for 2 transcriptional activators. (b) In copurifications from nonproliferating P17 cells (37°C) only 2 known AR-interacting proteins identified were components from the WINAC complex: SMARCA4 and ARID1A. However, 4 proteins identified: EP300, NCOA2, MED1, and SRC1* act as transcriptional activators in VDR, mediated gene expression. Under nonproliferating conditions, AR would therefore compete with VDR for 2 WINAC components and 4 transcriptional activators. *SRC1 is a general transcription activator for steroid receptors and also component of this pathway. SRC1 was not identified by mass spectrometry, but AR-associated in Western blots of FLAG-purifications from nuclear extracts of proliferating and nonproliferating P17 cells (Figures 4 and 3(b)).