RESUMO
While mammalian DNA polymerase ß (Pol ß), which is a member of the Pol X family, play important roles in base excision repair (BER) that efficiently removes DNA base lesions arising from both endogenous and exogenous agents, this protein has been found only a subset of animals. To understand natural evolution of this enzyme, we isolated and characterized Pol ß from jellyfish Aurelia sp.1. (AsPol ß). Despite of phylogenetic distance and environmental differences between jellyfish and mammals, in vitro assays showed biochemical characteristics of AsPol ß were very similar to those of a mammalian counterpart. We also searched two other homologs of mammalian genes that were involved in short patch (sp) BER in the nucleotide sequence database, and found that both of these homologs were encoded in the genomes of a lineage from Cnidarians through mammals and Arthropods. This study suggests that a DNA repair mechanism resembling mammalian sp-BER may be largely limited to a subset of animals. On the basis of our findings and previous reports, we discuss possible evolutional model of Pol ß and the other members of the Pol X family.
Assuntos
DNA Polimerase beta/metabolismo , Reparo do DNA , Cifozoários/enzimologia , Sequência de Aminoácidos , Animais , DNA Ligase Dependente de ATP , DNA Ligases/química , DNA Ligases/genética , DNA Ligases/metabolismo , DNA Polimerase beta/química , DNA Polimerase beta/classificação , DNA Polimerase beta/genética , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Evolução Molecular , Dados de Sequência Molecular , Filogenia , Proteínas de Ligação a Poli-ADP-Ribose , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Proteína 1 Complementadora Cruzada de Reparo de Raio-X , Proteínas de XenopusRESUMO
An excess of nonsynonymous substitutions over synonymous ones has been regarded as an important indicator of adaptive evolution or positive selection at the molecular level. We now report such a case for rbcL sequences among cryptic species in Conocephalum (Hepaticae, Bryophytes). This finding can be regarded as evidence of adaptive evolution in several cryptic species (especially in F and JN types) within the genus. Bryophytes are small land plants with simple morphology. We can therefore expect the existence of several biologically distinct units or cryptic species within each morphological species. In our previous study, we found three rbcL types in Asian Conocephalum japonicum (Thunb.) Grolle and also found evidence strongly suggesting that the three types are reproductively isolated cryptic species. Additionally, we examined rbcL sequence variation in six cryptic species of C. conicum (L.) Dumort. previously recognized by allozyme analyses. As a result, we were able to discriminate the six cryptic species based only on their rbcL sequences. We were able to show that rbcL sequence variation is also useful in finding cryptic species of C. conicum.
