To investigate C/EBP-β phosphorylation sites that may be important for LPS-stimulated SerpinB2 proximal promoter activity (Fig. 8B), we co-expressed several C/EBP-β phospho-acceptor mutants in which the critical threonine or serine residue was mutated to an alanine, along with the pGLmP-539 murine SerpinB2 luciferase reporter in Cebpb−/− MEFs.