Bacteriophage T7 DNA Primase: A Multifunctional Enzyme Involved in DNA Replication

Since priming of DNA synthesis by RNA has been recognized to be a mechanism utilized by a wide variety of organisms, a great deal of work on the enzymology of DNA replication has been directed toward identifying and isolating proteins supposed to be involved in primer synthesis. We turned our attention to the replication system induced by bacteriophage T7 and eventually discovered that the product of the T7 gene 4 is such a novel primer-generating enzyme (Scherzinger and Klotz 1975). Genetic analyses (Studier 1969, 1972) show the T7 gene-4 protein to be essential for phage DNA replication in vivo. Based on its ability to synthesize oligoribonucleotide primers and to assist T7 DNA polymerase during the initial stage of primer extension, we proposed that the gene-4 protein be called T7 DNA primase (Scherzinger et al. 1977a,b). The new term “primase” has also been adopted to designate another primer-generating polymerase, the dnaG...