Cloning and Characterization of the Human Integrin β6 Gene Promoter

Abstract

The integrin β6 (ITGB6) gene, which encodes the limiting subunit of the integrin αvβ6 heterodimer, plays an important role in wound healing and carcinogenesis. The mechanism underlying ITGB6 regulation, including the identification of DNA elements and cognate transcription factors responsible for basic transcription of human ITGB6 gene, remains unknown. This report describes the cloning and characterization of the human ITGB6 promoter. Using 5′-RACE (rapid amplification of cDNA ends) analysis, the transcriptional initiation site was identified. Promoter deletion analysis identified and functionally validated a TATA box located in the region −24 to −18 base pairs upstream of the ITGB6 promoter. The regulatory elements for transcription of the ITGB6 gene were predominantly located −289 to −150 from the ITGB6 promoter and contained putative binding sites for transcription factors such as STAT3 and C/EBPα. Using chromatin immunoprecipitation assays, this study has demonstrated, for the first time, that transcription factors STAT3 and C/EBPα are involved in the positive regulation of ITGB6 transcription in oral squamous cell carcinoma cells. These findings have important implications for unraveling the mechanism of abnormal ITGB6 activation in tissue remodeling and tumorigenesis.

Integrin αvβ6 sets the stage for colorectal cancer metastasis

“…Integrins can be composed from 1 of 18 α-and 8 β-subunits to form 24 known heterodimer combinations ( Fig. 1a) [1,2]. Integrin subunits range from between 750 and 1000 amino acid residues in length and are constructed from several domains that are flanked by flexible linker regions, a membrane-spanning helix and a typically short, unstructured cytoplasmic tail (Fig.…”

“…Each α/β combination confers a particular binding specificity and consequential downstream signalling capabilities which underpin the structural and functional diversity of the integrin family (Fig. 1a) [1]. For example, heterodimers such as α5β1, αVβ3, αVβ5 and αVβ6 mediate cellular adhesion by binding to Arg-Gly-Asp (RGD) sequence motifs found within a number of abundant ECM proteins, such as fibronectin, vitronectin, fibrinogen and von Fig.…”

“…As such, an exciting development in β6 research has been the recent identification by Xu et al of the previously unknown DNA elements and cognate transcription factors responsible for transcription of the β6 coding sequence (ITGB6, Fig. 3) [1].…”

“…Interestingly, Xu et al determined that mutation of the cMyb and AP1-binding sites did not exert significant effects on promoter activity [1]. They employed 5′-rapid amplification of cDNA ends (5′-RACE) to determine that the transcriptional Fig.…”

“…They employed 5′-rapid amplification of cDNA ends (5′-RACE) to determine that the transcriptional Fig. 2 Duke's and Tumour-Node-Metastasis staging systems with respective survival data from the European Society for Medical Oncology [72] start site was located 204 bp upstream of the ATG translation initiation site [1]. They then investigated the β6 promoter by cloning a series of truncated 5′-deletion fragments within the 5′-flanking region of the ITGB6 coding sequence into pGL2-Basic promoter-deficient luciferase reporter vectors [1].…”