Multiple Regulatory Regions and Tissue Specific Transcription Initiation Mediate the Expression of NEMO/IKKg Gene

NEMO/IKK? gene, which is responsible of two allelic diseases in human, EDA-ID and IP, encodes for a protein with a central regulatory role in the activation of the NF-kB pathway. We here provide insights into the molecular mechanism governing NEMO/IKK? expression. We mapped 4 distinctive NEMO/IKK? transcription start sites each corresponding to an alternative first exon, controlled by two conserved promoters. A distal promoter, named promoter A, located 10 kb upstream of the coding region and a proximal promoter, promoter B, with strong bi-directional activity driving also the transcription of G6PD gene in the opposite direction. The promoter B is housekeeping, it is embedded in a CpG island, required for proper expression and it is down-regulated by methylation. The promoter A is active in cells of hepatic origin and it directs transcription of the main NEMO/IKK? 5? UTR alternative transcript in liver, which starts at a tissue-specific site. Qualitative and quantitative expression analysis revealed that each NEMO/IKK? 5? UTR alternative transcript has different expression profiles indicating that the control of NEMO/IKK? expression is mediated through tissue-specific transcription initiation sites and multiple regulatory regions. © 2006 Elsevier B.V. All rights reserved.