Promoter characterization and genomic organization of the gene encoding integrin-linked kinase 1.

Integrin-linked kinase (ILK)-1 is a 59-kDa serine-threonine protein kinase, which associates with the cytoplasmic domain of beta 1, beta 2 and beta 3 integrins and acts as a receptor proximal kinase regulating integrin-mediated signal transduction. We have recently identified an isoform of ILK (ILK-2), which is expressed, in a TGF-beta 1-dependent manner, in a highly invasive tumor cell line but not in normal adult tissues. In contrast, ILK-1 is ubiquitously expressed in normal tissues and is up-regulated in various tumors independent of TGF-beta 1. Here, we report the structural organization and the promoter activity of the human ILK-1 gene, contained within a 8.8-kb genomic fragment cloned from a human BAC library. The mature protein is encoded by 13 exons. The last coding exon contains the entire 3' UTR of the ILK-1 gene, which overlaps with the complementary 3' UTR sequence of the TAF2H gene, a TATA box binding protein-associated factor. A major transcriptional initiation start site was found 138 bp upstream of exon 1 in close proximity to a consensus initiator element (Inr). The ILK gene is transcribed by a TATA-less and CAAT-less promoter with typical features of housekeeping genes. The promoter activity was characterized by a luciferase reporter assay and the minimal sequence conferring promoter activity was 349 bp in size and located immediately upstream of exon 1.