Hisao Masai and Ken-ichi Arai.

Department of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, 4-6-1, Shirokanedai, Minato-ku, Tokyo, 108, Japan

Received 01/17/96; Accepted 02/17/96; On-line 03/01/96

The process of DNA replication requires assembly of a replication complex, primosome, at the origin. The primosome is believed to be responsible for primer RNA synthesis of lagging strand and for duplex DNA unwinding, which are mediated by primase and DNA helicase, respectively, present in the protein complex. In conjunction with twin DNA polymerases and a swiverase which relieves torsional tension accumulating in advance of a replication fork, a primosome may contribute to efficient concurrent replication of leading and lagging strands at a replication fork. The molecular architecture of the primosomes have been studied in most detail in E. coli, leading to discovery of two structurally distinct primosomes. Molecular genetic analyses of protein components of the primosomes revealed their biological function of these protein complexes in replication of the E. coli chromosome as well as in that of plasmid replicons.