Genomic organization of the gene coding for human pre-B-cell colony enhancing factor and expression in human fetal membranes

Pre-B-cell colony enhancing factor (PBEF) was first isolated from an activa ted peripheral blood lymphocyte cDNA library and was found to be involved i n the maturation of B-cell precursors. It was subsequently identified as on e of the genes upregulated by distending the human fetal membranes in vitro . Here we report on the genomic organization of this gene, which is compose d of 11 exons and 10 introns, spanning 34.7 kb of genomic DNA. Neither the gene nor the protein has any homology with other cytokines in any currently available database. The use of two promoters (proximal and distal) may res ult in differential, tissue specific expression of the PBEF transcripts. Th e 5'-flanking region lacks the classical sequence motif that would place it with the hematopoietic cytokines; however, it has several putative regulat ory elements, suggesting that this gene may be chemically and mechanically responsive to inducers of transcription. The three PBEF mRNA transcripts were observed in both normal and infected h uman fetal membranes but were significantly upregulated (P<0.05) in severe infection. The PBEF protein was immunolocalized, in both normal and infecte d tissues, to both the normal fetal cells of the amnion and chorion and the maternal decidua of the membranes, and to the invading neutrophils. These stained strongly and were likely to contribute to the increased expression in infection. The amniotic epithelial cell line (WISH cells) has been used as a model to study PBEF gene modulation. Lipopolysaccharide, interleukin ( IL)-1<beta>, tumour necrosis factor (TNF)alpha and IL-6 all significantly i ncreased the expression of PBEF in 4h of treatment. The addition of dexamet hasone to IL-1 beta and TNF alpha significantly reduced the response of PBE F to these cytokines. IL-8 treatment failed to alter PBEF gene expression. Thus PBEF is a cytokine expressed in the normal fetal membranes and upregul ated when they are infected. It is likely to have a central role in the mec hanism of infection-induced preterm birth.