title: Cloning of a marsupial DNA photolyase gene and the lack of related nucleotide sequences in placental mammals.
abstract: Photoreactivating enzyme, DNA photolyase, reduces lethal, mutagenic and carcinogenic effects of ultraviolet light (UV) by catalyzing near UV or visible light-dependent repair of cyclobutane pyrimidine dimers (CPDs) in DNA. The enzyme activity has been detected in a wide variety of organisms ranging from bacteria to nonplacental mammals. However, the evidence for photoreactivation in placental mammals, including humans, is controversial. As a first step to identify the presence and activity of the gene in mammalian species, we isolated a cDNA clone of this gene from a marsupial, the South American opossum Monodelphis domestica. Photolyase activity was expressed in Escherichia coli from the cDNA which is predicted to encode a polypeptide of 470 amino acid residues. The deduced amino acid sequence of this protein is strikingly similar to those of photolyases from two metazoans; the opossum photolyase shares 59% and 63% sequence identity with the Drosophila melanogaster and goldfish Carassius auratus enzymes, respectively. However, no closely related nucleotide sequence was detected in higher mammals and a homologous transcript was undetectable in a number of human tissues. These results strongly suggest that humans, as well as other placental mammals, lack the photolyase gene.
authors.affiliation: Radiation Biology Center, Kyoto University, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kato
authors.forename: T
authors.initials: T
authors.lastname: Todo
authors.forename: H
authors.initials: H
authors.lastname: Ayaki
authors.forename: K
authors.initials: K
authors.lastname: Ishizaki
authors.forename: T
authors.initials: T
authors.lastname: Morita
authors.forename: S
authors.initials: S
authors.lastname: Mitra
authors.forename: M
authors.initials: M
authors.lastname: Ikenaga
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000737:chemistry / Q000235:genetics*; D004331:Drosophila melanogaster / Q000201:enzymology; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D006054:Goldfish; D006801:Humans; D008969:Molecular Sequence Data; D009893:Opossums / Q000235:genetics*; D010920:Placenta; D011994:Recombinant Proteins / Q000737:chemistry; D017385:Sequence Homology; D013045:Species Specificity; D014466:Ultraviolet Rays
chemical_list: D018076:DNA, Complementary; D011994:Recombinant Proteins; D004255:Deoxyribodipyrimidine Photo-Lyase