TRANSCRIPTION FROM PLASMID EXPRESSION VECTORS IS INCREASED UP TO 14-FOLD WHEN PLASMIDS ARE TRANSFECTED AS CONCATEMERS

A protocol for increasing transcription from plasmid expression vector s is presented. A vector containing chloramphenicol acetyltransferase (CAT) gene was digested leaving the transcription cassette intact. Hea t inactivation of restriction enzymes followed by ligation of the dige stion products yielded concatemers which migrated as a single band in agarose gel electrophoresis. Mouse fibroblasts transfected with the co ncatemers gave a CAT activity that was 14-fold greater than that of ce lls transfected with a similar mass (equimolar gene number) of the nat ive plasmid. The effect was independent of promoter type, restriction enzyme, number of restriction sites and with a noted exception, cell l ine.