A beta-galactosidase expression vector for promoter analysis.

An expression vector plasmid, designated pMCS beta gal, was constructed to contain a multiple cloning site for insertion of gene fragments with potential regulatory function. This plasmid was designed to test promoter activity in transgenic mice, since digestion with Pst I will release all vector sequences, which could inhibit transgene expression in vivo (Jaenisch, 1988). When this vector, containing the amelogenin promoter, was used to make transgenic mice, expression was tissue specific and developmentally regulated similar to the endogenous gene (Chen et al., 1994). In addition, the herpes simplex virus (HSV) thymidine kinase (TK) minimal promoter was inserted into pMCS beta gal to produce pTK beta gal, leaving an Sph I upstream site available for insertion of gene fragments with potential enhancer or silencer function, which can be assayed following transfection into cultured cells.