The effect of interleukin-1 on C-reactive protein expression in Hep3B cells is exerted at the transcriptional level.
The combination of interleukin 6 (IL-6) and interleukin 1 (IL-1) synergistically induces the human acute-phase reactant, C-reactive protein (CRP) in Hep3B cells. While previous studies have indicated that IL-6 induces transcription of CRP, the mode of action of IL-1 has not been clearly defined. It has been suggested that the effect of IL-1 might be post-transcriptional, exerted through the 5'-untranslated region (5'-UTR). To evaluate the role of IL-1 in CRP gene expression, we studied the effects of interleukin-6 (IL-6) and interleukin-1 beta (IL-1 beta) on both the endogenous CRP gene and on transfected CRP-CAT constructs in Hep3B cells. In kinetic studies of the endogenous CRP gene, IL-1 beta alone had no effect on CRP mRNA levels, but when added to IL-6, synergistically enhanced both CRP mRNA levels and transcription, as determined by Northern-blot analyses and nuclear run-on studies. IL-6 alone and the combination of [IL-1 beta + IL-6] each induced increases in mRNA levels roughly comparable with observed increases in transcription. These findings indicate that the effect of IL-1 beta on CRP expression is exerted largely at the transcriptional level in this system. This conclusion was confirmed by studies in Hep3B cells transiently transfected with CRP-CAT constructs, each containing 157 bp of the CRP 5'-flanking region but differing in the length of the 5'-UTR from 104 bp to 3 bp. All constructs responded in the same way; IL-6, but not IL-1 beta, induced significant chloramphenicol acetyltransferase (CAT) expression which was synergistically enhanced 2- to 3-fold by IL-1 beta. These results indicate that IL-1 beta stimulates transcriptional events in the presence of IL-6 and that the upstream 157 bases of the CRP promoter contain elements capable of both IL-6 induction and the synergistic effect of IL-1 beta on transcription.
Zhang
D
D
Department of Biochemistry, Case Western Reserve University, Cleveland, OH, USA.
Jiang
S L
SL
Rzewnicki
D
D
Samols
D
D
Kushner
I
I
D002097:C-Reactive Protein / Q000235:genetics* / Q000378:metabolism; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology*; D015850:Interleukin-6 / Q000494:pharmacology; D011499:Protein Processing, Post-Translational; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects*; D014407:Tumor Cells, Cultured
D007375:Interleukin-1; D015850:Interleukin-6; D012333:RNA, Messenger; D002097:C-Reactive Protein; D015500:Chloramphenicol O-Acetyltransferase