A Novel DNA Polymerase Family Found in Archaea
Yoshizumi ISHINO*a and Kayoko KOMORIa, Isaac K. O. CANNa, and Yosuke KOGAb
a Department of Molecular Biology, Biomolecular Engineering Research Institute (BERI), 6- 2-3 Furuedai, Suita, Osaka 565, Japan
b Department of Chemistry, University of Occupational and Environmental Health, 1- Isegaoka, Yahata-nishi-ku, Kitakyushu 807, Japan
DNA polymerases play leading roles in cellular DNA replication and repair. They can be classified into four major groups based on the amino acid sequences (1). Family A includes the most abundant DNA polymerases in eubacterial cells such as E. coli DNA polymerase I. All of the replicative DNA polymerases from eukaryotic and eubacterial cells belong to Families B and C, respectively. Family X consists of eukaryotic DNA polymerase β and terminal transferases. All of the sequences of the archaeal DNA polymerases have been classified as Family B (α-like) DNA polymerases.
One of the most puzzling result from the complete genome sequence of the methanogenic archaeon, Methanococcus jannaschii was that the organism may have only one DNA polymerase gene. This is because no other DNA polymerase-like open reading frames (ORFs) were found besides one ORF having the typical α-like DNA polymerase. Recently, we identified the gene of DNA polymerase II (the second DNA polymerase) from the hyperthermophilic archaeon, Pyrococcus furiosus, which has also at least one α-like DNA polymerase (2). A gene in M. jannaschii encoding the protein that is homologous to the DNA polymerase II of P. furiosus has been located and cloned. The gene product of M. jannaschii expressed in Escherichia coli had both DNA polymerizing and 3'→5' exonuclease activities. We have also detected genes within Pyrococcus wosei that encode homologous proteins. We propose here a novel DNA polymerase family which is entirely different from other hitherto described DNA polymerases.
1. Ito, J. and Braithwaite, D.K. (1991) Nucleic Acids, Res., 19, 4045-4057.
2. Uemori, T., Sato, Y., Kato, I., Doi, H. and Ishino, Y. (1996) Genes to Cells, 2, 499-512
