Functional role of NF-IL6beta and its sumoylation and acetylation modifications in promoter activation of cyclooxygenase 2 gene

NF-IL6beta regulates gene expression and plays function roles in many tissues. The EGF-regulated cyclooxygenase-2 (COX-2) expression is mediated through p38(MAPK) signaling pathway and positively correlates with NF-IL6beta expression in A431 cells. NF-IL6beta coordinated with c-Jun on COX-2 transcriptional activation by reporter and small interfering RNA assays. NF-IL6beta could directly bind to CCAAT/enhancer-binding protein (C/EBP) and cyclic AMP-response element (CRE) sites of the COX-2 promoter by in vitro-DNA binding assay. The C/EBP site was important for basal and, to a lesser extent, for EGF-regulated COX-2 transcription, while the CRE site was a more specific response to EGF inducibility of COX-2 gene. SUMO1 expression attenuated EGF- and NF-IL6beta-induced COX-2 promoter activities. NF-IL6beta was found to be sumoylated by in vivo- and in vitro-sumoylation assays, and the SUMO1-NF-IL6beta (suNF-IL6beta) lost its ability to interact with p300 in in vitro-binding assay. NF-IL6beta was also acetylated by p300, and acetylation of NF-IL6beta enhanced the COX-2 promoter activity stimulated by NF-IL6beta itself. In vivo-DNA binding assay demonstrated that EGF stimulated the recruitment of p300 and NF-IL6beta to the COX-2 promoter, yet promoted the dissociation of SUMO1-modificated proteins from the promoter. These results indicated that NF-IL6beta plays a pivotal role in the regulation of basal and EGF-induced COX-2 transcription.