A refined vector system for the in vitro construction of single-copy transcriptional or translational fusions to lacZ.

New single-copy vectors based on lambda phage have been developed for creating either transcriptional (operon) or translational (gene) fusions to the lacZ gene. The improvements of these vectors over the previous lambda TL61 vector include: (i) incorporation of a tetracycline-resistance-encoding gene (TcR) to permit direct selection of lysogens, (ii) low-background beta-galactosidase activity, (iii) the ability to accept DNA inserts up to 8 kb in size, and (iv) an expanded multiple cloning site (MCS). The new transcriptional fusion vector retains the RNase III processing site downstream from the MCS which ensures independent translation of lacZ. The set of three translational fusion vectors allow for convenient subcloning in any of the three translational reading frames.