Cell-free expression of the beta-galactosidase gene: a model system to study the effects of nucleotide analogs on transcription-translation.

A cell-free system for the expression of the beta-galactosidase gene was employed to study the effects of the UTP and CTP analogs: s2UTP, s2CTP, f5UTP and rTTP on transcription-translation. From the analogs investigated, only rTTP turned out to be able to substitute UTP in the cell-free synthesis of beta-galactosidase. In case of the other analogs listed above, the incorporation of even a small fraction of analog into rRNA resulted in drastic inhibition of beta-galactosidase synthesis.