Multiple cis-acting elements in the IGRP promoter are required for maximal basal reporter gene expression in βTC-3 cells. βTC-3 cells were transiently cotransfected (as described in the research design and methods) with an expression vector encoding renilla luciferase (0.5 μg) and with a series of IGRP-CAT fusion genes (2 μg) with 5′ deletion end points between −306 and −197 (A) or −197 and −66 (B). Multiple cis-acting elements in the IGRP promoter are required for maximal basal reporter gene expression in βTC-3 cells. βTC-3 cells were transiently cotransfected (as described in the research design and methods) with an expression vector encoding renilla luciferase (0.5 μg) and with a series of IGRP-CAT fusion genes (2 μg) with 5′ deletion end points between −306 and −197 (A) or −197 and −66 (B). After transfection, cells were incubated for 18–20 h in serum-containing medium. The cells were then harvested and both CAT and luciferase activity assayed as previously described (21, 28). Results are presented as the ratio of CAT:luciferase activity and represent the mean of three experiments ± SE, each using an independent preparation of each 5′ truncated fusion gene plasmid. Larry J. Bischof et al. Diabetes 2001;50:502-514 ©2001 by American Diabetes Association