Control of core 2 beta1,6 N-acetylglucosaminyltransferase-I transcription by Sp1 in lymphocytes and epithelial cells

Abstract

Core 2 beta1,6 N-acetylglucosaminyltransferase-I (C2GnT-I) catalyzes the synthesis of one of the major core structures in GalNAc alpha-Ser/Thr O-linked oligosaccharides, the core 2 branch. The production of the core 2 branch is required for the synthesis of glycoforms that are important for the cellular functions of lymphocytes, mucin-producing epithelial cells and other cell types. Therefore, proper molecular control of C2GnT-I expression is very important for different types of cells. C2GnT-I is transcribed from 4 promoters, with promoter 2 being the major promoter. C2GnT-I promoter 2 lacks a TATA box and is very GC rich. In this study, the analysis of this promoter finds that the transcription factor Sp1 is essential for transcription of C2GnT-I in both mesodermally derived T-cells (Jurkat) and in endodermal mucin producing epithelial cells (NCI H292). In Jurkat cells, all nine of the Sp1 binding sites within the minimal promoter region contribute to transcription, and there is a linear relationship between the number of Sp1 sites and the transcriptional activity of the promoter. In NCI H292 cells, only three of these Sp1 binding sites are required for transcription from promoter 2. Chromatin immunoprecipitation confirms that Sp1 binds to promoter 2 in NCI H292 cells in vivo.