Characterization of the promoter of 1A6/DRIM, a novel cancer-related gene and identification of its transcriptional activator.

1A6/DRIM (Down-regulated in Metastasis) has been reported to express at a high level in the gastric cancer tissues and the premalignant lesions implicating the involvement of 1A6/DRIM in cell transformation. Although the information regarding the putative functions and distribution of the 1A6/DRIM in different tissues and cell lines has been increasing recently, its promoter and promoter-regulating factors remain unknown. In this study, the transcription initiation site of 1A6/DRIM was confirmed to be located at 147 bp upstream of the ATG codon using the primer extension analysis. The minimal promoter region of the 1A6/DRIM is located between -47 and +42 of the transcription initiation site measured by luciferase reporter assays using a set of deletion constructs. In addition, an E-box is shown to be an essential element for transcriptional regulation of 1A6/DRIM demonstrated by luciferase assay with different deletion and mutation constructs. Finally, a transcription factor, upstream stimulatory factor 2 (USF2) was found to be an activator of the 1A6/DRIM through binding to the E-box demonstrated by luciferase reporter assay, electrophoretic mobility shift assay, and chromatin immunoprecipitation (ChIP) assay. The structural analysis of the 1A6/DRIM promoter and the identification of its potential regulatory effecter may help us to understand its biological functions in regulating cancer development.