Integrated Genetics, 31 New York Avenue, Framingham, MA 01701.
Human tissue-type plasminogen activator (t-PA) cDNA was cloned from uterine tissue and engineered in expression vectors for production in mouse C127 cells. The vectors consisted of the bovine papilloma virus-1 (BPV-1) genome and t-PA transcriptional unit with a mouse metallothionein (MT-1) promoter at the 5' end and MT-1 genomic sequences or SV40 early introns and polyadenylation signals at the 3' end. Analysis of the expression vectors transfected into cells revealed that t-PA is expressed 100- to 200-fold more with an intronless vector utilizing the SV40 polyadenylation signal than with other, intron-containing vectors. RNA analysis of stable cell lines indicated that t-PA expression levels correlated with mRNA abundance. DNA copy number and transcriptional rate of the MT-1 promoter remained constant in cell lines transformed by different BPV expression vectors. Uterine t-PA produced by recombinant DNA means was enzymatically active and similar in properties to Bowes melanoma t-PA.