DEVELOPMENTAL REGULATION OF BETA-GALACTOSIDE ALPHA-2,6-SIALYLTRANSFERASE IN SMALL-INTESTINE EPITHELIUM

A striking biochemical alteration to the epithelium of the small intes tine upon weaning is the loss of microvillar sialic acids. Antibody an d cDNA probes to the beta-galactoside alpha 2,6-sialyltransferase (Sia T-1, EC 2.4.99.1) were used to characterize the expression of this sia lyltransferase in the small intestine of suckling rats. SiaT-1 mRNA an d protein in the intestinal epithelium are rapidly lost upon weaning, in agreement with the loss of mucosal sialic acids and general sialylt ransferase activity. Developmental repression of SiaT-1 is manifested in a proximal to distal gradient; SiaT-1 mRNA and protein are lost fir st from the duodenum and persist the longest in the ileum. We have pre viously documented that SiaT-1 gene expression can be transcriptionall y initiated from a number of distinct tissue-specific promoter regions . Here, by criteria of mRNA mobility on agarose gels, primer extension analysis, and differential Northern hybridization, we show that the p romoter previously considered to be liver-specific is operative in Sia T-1 expression in the small intestine of suckling animals. Comparison of this SiaT-1 promoter region with promoter regions of other genes ex hibiting dual intestine-hepatic tissue specificity revealed a number o f striking sequence similarities. Regulatory implications and conseque nces of small intestinal SiaT-1 expression in suckling but not in wean ed animals are discussed. (C) 1994 Academic Press, Inc.