Cebpb−/− MEFs were co-transfected with expression plasmids encoding wild-type C/EBP-β or the indicated C/EBP-β phospho-acceptor mutants, along with the pGLmP-539 SerpinB2 promoter-luciferase reporter and β-galactosidase reporter plasmids, and stimulated with LPS for 4 hrs.