a, Mediator and Cohesin components were highly represented in an shRNA screen for regulators of ES cell state. Complete results are listed in Supplementary Tables 1, 2. b, Knockdown of Mediator (Med12), Cohesin (Smc1a) or Nipbl caused reduced Oct4 protein levels and changes in ES cell colony morphology. Murine ES cells were infected with GFP control, Med12, Smc1a or Nipbl shRNAs, and stained for Oct4 and with Hoechst. Scale bar = 100μM. c, Mediator, Cohesin and Nipbl knockdowns all cause reduced expression of ES cell regulators and increased expression of developmental regulators. ES cells were infected with the indicated shRNA and gene expression levels relative to a control GFP infection were determined with microarrays. Log2 fold expression changes were rank ordered from lowest to highest for all genes.