Promoters recognized by Escherichia coli RNA polymerase selected by function: highly efficient promoters from bacteriophage T5.

Highly efficient promoters of coliphage T5 were identified by selecting for functional properties. Eleven such promoters belonging to all three expression classes of the phage were analyzed. Their average AT content was 75% and reached 83% in subregions of the sequences. Besides the well-known conserved sequences around -10 and -33, they exhibited homologies outside the region commonly considered to be essential for promoter function. Interestingly, the consensus hexamers around -10 (TAT AAT) and -35 (TTG ACA) were never found simultaneously within the sequence of highly efficient promoters. Several of these promoters compete extremely well for Escherichia coli RNA polymerase and can be used for the efficient in vitro synthesis of defined RNA species. In addition, some of these promoters accept 7-mGpppA as the starting dinucleotide, thus producing capped mRNA in vitro which can be utilized in various eucaryotic translation systems.