Activity assays of nine heterogeneous promoters in neural and other cultured cells

Summary To express high levels of proteins encoded by transfected DNA constructs in a variety of cultured cells, including neuronal cells, the activities of nine different promoters were evaluated usingEscherichia coli β-galactosidase (β-gal) (LacZ) as a reporter gene. These nine promoters were categorized into three distinct groups (high, intermediate, and low expresser), in terms of the levels ofβ-gal expression. An expression vector containing the cytomegalovirus enhancer and the chickβ-actin promoter (high expresser) showed the highest levels of expression, followed by vectors containing the cytomegalovirus promoter/enhancer and the SV40 promoter/enhancer (intermediate expresser). The rest of the promoters (thymidine kinase, adenovirus, murine proliferative sarcoma virus, nerve growth factor receptor, Rous sarcoma and mouse mammary tumor virus, andβ-amyloid precursor protein) expressed low levels ofβ-gal. These results were consistent for eight different cell types. A particularly attractive model is the stem cell, P19; cultures differentiating into progeny consisting predominantly of cholinergic neurons could be readily transfected with expression vectors using liposomes and expressedβ-gal without significant morphologic changes of the differentiated neurons. The systems should be useful for the study of promoters and various expressed proteins, including those involved in axonal transport.