Transcription of RNA templates by T7 RNA polymerase

Although highly specialized, T7 RNA polymerase seems to possess a large range of DNA- and RNA-dependent properties. To study such flexibility, we determined the ability of T7 RNA polymerase to transcribe chimeric DNA-RNA and RNA templates following initiation at a double stranded DNA promoter. We have found that T7 RNA polymerase is able to initiate on RNA templates, was processive, and was able to use templates containing RNA-RNA duplexes under standard transcription conditions. Implications of remnants of such RNA-dependent activities for T7 DNA-dependent polymerase are discussed.