Serotonin-inducible transcription of interleukin-1 alpha in uterine smoothmuscle cells requires an AP-1 site: cloning and partial characterization of the rat IL-1 alpha promoter

Interleukin-1 has been shown to contribute to infection-induced inflammator y processes during pregnancy. Prior work from this laboratory has demonstra ted that serotonin-induced IL-1 alpha also is required for the in-vitro pro duction of collagenase in uterine smooth muscle cells, a normal, non-inflam matory process that occurs in-vivo during post-partum uterine involution. T o understand the molecular mechanisms that regulate transcription of the IL -1 alpha gene in these cells, we isolated and characterized 1.6 kilobases o f the 5'-flanking region of the rat IL-1 alpha gene. Sequencing and primer extension identified a single transcription start site and multiple potenti al regulatory elements, including a TATA box at - 30 bp, a CAAT box at - 74 bp, and a conserved AP-1 site at -9 bp. This 5'-flanking DNA exhibited low basal promoter activity that was inducible by serotonin. Serotonin-induced promoter activity was unaffected or induced by either medroxyprogesterone or IL-1 receptor antagonist. This occurred despite the ability of both of t hese hormones to markedly decrease IL-1 alpha mRNA. Deletional analysis rev ealed a strong repressor in the region between -147 and -98 bp; removal of this sequence resulted in a fivefold higher basal promoter activity that wa s still serotonin responsive. Constitutive promoter activity appeared to re side between -97 and -22 bp. Deletion of this promoter region, which contai ned the TATA and CAAT boxes and an NF-IL-6/PEA-3 site, resulted in decrease d basal transcriptional activity to the low level seen in larger constructs . Mutational analysis showed that serotonin-inducible transcriptional activ ity was mediated, at least in part, by the conserved AP-I site at -9 bp. Th is site is located within a larger extended palindromic region: 5'-AAGCCTGA CTCAGACTT-3', that together effects both the basal and serotonin-inducible expression of the IL-1 alpha gene. (C) 1999 Elsevier Science Ireland Ltd. A ll rights reserved.