title: Evidence of independent gene duplications during the evolution of archaeal and eukaryotic family B DNA polymerases.
abstract: Eukaryotes and archaea both possess multiple genes coding for family B DNA polymerases. In animals and fungi, three family B DNA polymerases, alpha, delta, and epsilon, are responsible for replication of nuclear DNA. We used a PCR-based approach to amplify and sequence phylogenetically conserved regions of these three DNA polymerases from Giardia intestinalis and Trichomonas vaginalis, representatives of early-diverging eukaryotic lineages. Phylogenetic analysis of eukaryotic and archaeal paralogs suggests that the gene duplications that gave rise to the three replicative paralogs occurred before the divergence of the earliest eukaryotic lineages, and that all eukaryotes are likely to possess these paralogs. One eukaryotic paralog, epsilon, consistently branches within archaeal sequences to the exclusion of other eukaryotic paralogs, suggesting that an epsilon-like family B DNA polymerase was ancestral to both archaea and eukaryotes. Because crenarchaeote and euryarchaeote paralogs do not form monophyletic groups in phylogenetic analysis, it is possible that archaeal family B paralogs themselves evolved by a series of gene duplications independent of the gene duplications that gave rise to eukaryotic paralogs.
authors.affiliation: Canadian Institute for Advanced Research, Department of Biochemistry, Dalhousie University, Halifax, Nova Scotia, Canada. buddy@csc.albany.edu
authors.forename: D R
authors.initials: DR
authors.lastname: Edgell
authors.forename: S B
authors.initials: SB
authors.lastname: Malik
authors.forename: W F
authors.initials: WF
authors.lastname: Doolittle
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001105:Archaea / Q000201:enzymology / Q000235:genetics*; D001483:Base Sequence; D017931:DNA Primers; D004259:DNA-Directed DNA Polymerase / Q000235:genetics*; D019143:Evolution, Molecular; D016829:Giardia lamblia / Q000201:enzymology / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D014246:Trichomonas vaginalis / Q000201:enzymology / Q000235:genetics*
chemical_list: D017931:DNA Primers; D004259:DNA-Directed DNA Polymerase