Gene Transfer and Expression

DNA transfection has become an important technique in molecular biology. The fusion of putative gene-regulatory sequences to reporter genes and their introduction into a eukaryotic cell can be used for a detailed analysis of cisacting DNA regulatory sequences (1 ). DNA regulatory elements such as those responsive to CAMP (2 ) or to glucocorticoids and antiglucocorticoids (3 ) as well as to drugs and xenobiotics such as phenobarbital (4 , 5 ) can be identified through the use of approprtate reporter-gene constructs. Cotransfection experi-ments with vectors expressing specific transcription factors can be used to iden-tify the role of these transcription factors in the expression of specific genes (6 ) and in addition, the developmental activation of a promoter can be examined (7 ). The expression of functional protein in transfected cells can be useful for studies on genetic toxicology (8 ) or biochemical pathways (9 ). By the intro-duction of mutated DNAs that produce modified protems in the transfected cell, the functional significance of protein domains (10 ) and individual aminoacid residues (11 , 12 ) can be elucidated, and the transfection of cDNAs isolated from patients has already proved useful for the analysis of molecular defects that result in genetic disorders (13 ).