C/EBPα Is Critical In TNFα Mediated Regulation Of The Human Calreticulin Promoter

Calreticulin (CRT) is a ubiquitously expressing Ca 2+ binding chaperone protein in the endoplasmic reticulum (ER). An earlier study from our laboratory had shown that elevated levels of TNFα that are hallmarks of diverse metabolic diseases down‐regulates CRT gene expression. Here, we reasoned to decipher the mechanisms behind this regulation. Experiments were performed using luciferase reporter constructs harboring the complete and deleted regions of the CRT promoter. In addition, EMSA and CHIP experiments were done to assess the occupancy of the CRT promoter by transcription factors. We demonstrate that the −1.0kb to −0.5kb region is critical in dictating the CRT promoter activity. Of the transcription factors that possess binding elements within this region, C/EBPα was identified as being crucial in mediating, at least in part, the inhibitory effect of TNFα. The inhibitory effect of TNFα on the wild‐type CRT promoter construct was effectively abrogated in a construct lacking the C/EBPα binding site. In the presence of TNFα, C/EBPα occupancy on the CRT promoter is significantly reduced together with decreased binding of the nuclear protein to the C/EBPα‐sequence. Based on our results, we suggest that C/EBPα is critical, at least in part, in mediating the inhibitory effect of TNFα on the CRT promoter that is presumably decisive in manifesting the deleterious effects of TNFα.