Transcriptional regulation of intercellular adhesion molecule 1 by phorbol ester in human neuroblastoma cell line SK-N-SH involves jun- and fos- containing activator protein 1 site binding complex(es)

In this study, the regulatory elements involved in ICAM-1 transcriptional response to phorbol ester (12-O-tetradecanoylphorbol-13- acetate; TPA) have been investigated in the human neuroblastoma cell line, SK-N-SH. TPA induced intercellular adhesion molecule 1 (ICAM-1) protein expression in SK-N-SH cells within 24 h of treatment as judged by indirect immunofluorescence. Basal ICAM-1 mRNA levels were barely detectable in untreated SK-N-SH cells but were induced by TPA to a maximal level within 4 h and were reduced thereafter. Analysis of the 5' promoter sequence of ICAM-1 revealed two regions that functioned equally in the TPA induction of ICAM-1 transcription. The first region (-145 to -227) contained a nuclear factor- κB (NFκB) element. The second region (-316 to -390) contained a putative TPA-responsive element (TRE; TGATTCA) and a TATA box. Deletion and point mutation of the latter region indicated that the TRE was indeed the functional element within this region and acted fully and independently of all other elements including the TATA box at position -352. This TRE bound TPA induced specific nuclear complexes in vitro containing junD, c-jun, c- fos, and fra2 but not cAMP-responsive element binding/activating transcription factor family proteins. ICAM-TRE binding activity was induced within 30 min following TPA treatment. This preceded the appearance of ICAM- NFκB site binding activity. Cotransfection of c-jun and c-fos expression vectors into SK-N-SH cells induced transactivation form ICAM-1 promoter constructs containing the intact but not mutated TRE site. Primer extension analyses revealed that TPA had induced transcription exclusively at two sites -40 and 41 bp upstream of the translation start site. These data show that the ICAM-TRE and its cognats jun- and fos-containing transcription factors play a predominant role in the transcriptional response of ICAM-1 to the protein kinase C activator TPA in SK-N-SH cells.