Transcriptional regulation of fibronectin gene by phorbol myristate acetate in hepatoma cells: A negative role for NF-κB

✍ Scribed by Byung-Heon Lee; Min-Seung Kim; Jung-Hwa Rhew; Rang-Woon Park; Benoit de Crombrugghe; In-San Kim

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 258 KB
• Volume: 76
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/(sici)1097-4644(20000301)76:3<437::aid-jcb11>3.0.co;2-2

✦ Synopsis

The transcriptional regulation of the fibronectin (FN) gene in hepatoma cells by phorbol myristate acetate (PMA) was investigated. PMA increased the synthesis and mRNA levels of FN and its promoter activity in Hep3B hepatoma cells. The PMA-induced activation of FN expression was blocked by a protein kinase C (PKC) inhibitor and did not require a new protein synthesis. Deletion analysis revealed that the sequence between positions Ϫ69 and ϩ136 of the FN gene was responsible for the PMA induction. Two PMA-inducible nuclear protein complexes were found to bind to a putative NF-B site at Ϫ41 and were identified as a p65/p50 heterodimer and a p50/50 homodimer of NF-B family. Mutations in the Ϫ41 NF-B site, however, did not block the PMA induction of the FN promoter but rather enhanced it. Overexpression of p65 increased the FN promoter activity. While overexpression of p50 alone did not affect the promoter activity, it decreased the p65-induced activation of the FN promoter. Mutations in the Ϫ41 NF-B site attenuated the p50-mediated suppression of the p65 transactivation of the FN promoter. Deletion of the sequence between ϩ1 and ϩ136 decreased the basal and PMA-induced activities of the FN promoter. This study shows that PMA induces the transcription of the FN gene in hepatoma cells via the PKC pathway. The DNA sequence between ϩ1 and ϩ136 is responsible, at least in part, for the PMA-induced activation of the FN gene, while the Ϫ41 NF-B binding site plays as a negative regulatory element for it. In addition, this study is the first to show a role for NF-B p65 in the transcriptional activation of the FN gene.