A LIMITED UPSTREAM REGION OF THE HUMAN SUCRASE-ISOMALTASE GENE CONFERS GLUCOSE-REGULATED EXPRESSION ON A HETEROLOGOUS GENE

We have previously shown that glucose can exert a repressive effect on the transcription of the sucrase-isomaltase (SI) gene in the differen tiated enterocyte-like human colon carcinoma cell lines HT-29 and Caco -2. To characterize the region through which glucose exerts this effec t, three different-length fragments of the 5'-flanking region of the h uman SI gene were linked to the reporter gene luciferase in an episoma l vector carrying a hygromycin resistance gene. These fragments were u sed for transfection into a clone of the Caco-2 cell line, PF11, which has high glucose consumption and only expresses SI at high levels whe n cultured in the presence of a low supply of glucose. By using the st ably transformed PF11 cells grown either in standard high glucose (25 mM) or in low glucose (1 mM) it was possible to show that the smallest fragment of the SI promoter, extending from bases -370 to +30, contai ns all the information required for the glucose repression of the repo rter gene luciferase.