The use of viral promoters in expression vectors

In genetics, promoters are nucleic acid sequences that lead to the initiation of transcription. They are directional signals that can vary in strength and complexity but their essential role is always the same, to ensure that RNA polymerase binds to the template and produces an RNA molecule for a functional outcome, most usually translation. Promoters are at heart of any expression vector, without them the downstream sequence, however well honed, will fail to fulfill its intended design. As a result, promoter choice is an integral part of vector construction. For reasons that reflect their underlying roles in virus replication cycles, the use of viral promoters features extensively in expression vectors, be they for mammalian, bacterial, plant or in vitro based systems. Their fundamental properties of regulation and strength dictate the circumstances under which they function and the amount of RNA they produce, both key aspects of expression vector design. In a curious contradiction, the study of viruses themselves generally relates to their pathogenicity but that of their component parts, notably virus promoters, is associated with productive and beneficial use