The role of CCAAT/enhancer-binding protein beta in the transcriptional regulation of COX-2 in human amnion.
Human labour is associated with increased prostaglandin synthesis within the uterus by the action of the inducible type-2 cyclo-oxygenase enzyme (COX-2). A major source of prostaglandin is the fetal membranes, in particular the amnion, in which expression of COX-2 increases in late pregnancy and with labour. The COX-2 gene promoter contains several putative transcription factor binding sites including those for NF-kappaB, AP-1 and C/EBP and therefore has the features of a rapid response gene. We have previously shown that, in amnion, the NF-kappaB DNA-binding sites in the COX-2 promoter are essential for gene expression and that there is an increase in NF-kappaB activity in amnion with the onset of labour. In this study, we demonstrate that in primary human amnion cells, CCAAT/enhancer-binding protein beta (C/EBPbeta) DNA-binding sites are crucial for the function of the COX-2 gene promoter. Three potential C/EBPbeta DNA-binding sites were identified within the COX-2 promoter which were shown to bind to C/EBPbeta but not to C/EBPalpha, C/EBPdelta, CREB (cAMP responsive element modulator) or CREM. Luciferase reporter constructs with site-directed mutagenesis of the three C/EBPbeta sites in the COX-2 promoter showed reduced expression of luciferase in transient transfection studies. However, comparison of C/EBPbeta protein levels and their DNA-binding activity from cells obtained before and after labour showed no significant differences. This suggests that although C/EBPbeta plays an essential constitutive role in the expression of COX-2, C/EBPbeta may not be directly involved in its regulation in association with human labour.
Lee
Yun S
YS
Imperial College Parturition Research Group, Institute of Reproductive and Developmental Biology, Hammersmith Hospital Campus, London, UK. yun.lee@imperial.ac.uk
Terzidou
Vasso
V
Lindstrom
Tamsin
T
Johnson
Mark
M
Bennett
Phillip R
PR
D000650:Amnion / Q000201:enzymology / Q000502:physiology*; D001483:Base Sequence; D001665:Binding Sites; D023081:CCAAT-Binding Factor / Q000502:physiology*; D002585:Cesarean Section; D051546:Cyclooxygenase 2 / Q000235:genetics*; D017931:DNA Primers; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D006801:Humans; D016297:Mutagenesis, Site-Directed; D011247:Pregnancy; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic; D014162:Transfection
D023081:CCAAT-Binding Factor; D017931:DNA Primers; D051546:Cyclooxygenase 2