MUTANTS OF T7 RNA-POLYMERASE THAT ARE ABLE TO SYNTHESIZE BOTH RNA ANDDNA

A mutant T7 RNA polymerase (T7 RNAP) having two amino-acid substitutio ns (Y639F and S641A) is altered in its specificity towards nucleotide substrates, but is not affected in the specificity of its interaction with promoter and terminator sequences. The mutant enzyme gains the ab ility to utilize dNTPs and catalyze RNA and DNA synthesis from circula r supercoiled plasmid DNA. DNA synthesis can also be initiated from a single stranded template using a DNA primer. Another T7 RNAP mutant ha ving only the single substitution S641A loses RNA polymerase activity but is able to synthesize DNA.