A proximal region of the G6Pase catalytic subunit promoter is sufficient for maximal basal reporter gene expression in HIT cells. A proximal region of the G6Pase catalytic subunit promoter is sufficient for maximal basal reporter gene expression in HIT cells. HIT cells were transiently cotransfected (as described in research design and methods) with an expression vector encoding βG (2.5 μg) and with a series of G6Pase catalytic subunit-CAT fusion genes (15 μg) with 5′ deletion end points between −751 and −85. After transfection, cells were incubated for 18–20 h in serum-free medium. The cells were then harvested and both CAT and βG activity assayed as previously described (21). Results are presented as the ratio of CAT:βG 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