Properties of the Primase Activity of the 9 S DNA Polymerase α from Calf Thymus

Abstract

Enzymes called primases are required for the initiation of DNA synthesis on the lagging strand of the replication fork. Primases are capable of synthesizing RNA primers from ribonucleoside triphosphates with single-stranded DNA as a template. In Escherichia coli, the primase has been identified and characterized (1). It is not part of the DNA polymerase III holoenzyme, the replicative DNA polymerase. In eukaryotes, a primase activity could be demonstrated to be part of a high molecular weight form of DNA polymerase a in several systems (2–7). We have recently described a 9 S DNA polymerase a from calf thymus that carries a catalytically active subunit of 148 kd and further subunits of 59, 55 and 48 kd (8). We now report the properties of a primase activity associated with the 9 S enzyme.