title: Transport of rice cyclobutane pyrimidine dimer photolyase into mitochondria relies on a targeting sequence located in its C-terminal internal region.
abstract: The cyclobutane pyrimidine dimer (CPD), which represents a major type of DNA damage induced by ultraviolet-B (UVB) radiation, is a principal cause of UVB-induced growth inhibition in plants. CPD photolyase is the primary enzyme for repairing CPDs and is crucial for determining the sensitivity of Oryza sativa (rice) to UVB radiation. CPD photolyase is widely distributed among species ranging from eubacteria to eukaryotes, and is classified into class I or II based on its primary structure. We previously demonstrated that rice CPD photolyase (OsPHR), which belongs to class II and is encoded by a single-copy gene, is a unique nuclear/mitochondrial/chloroplast triple-targeting protein; however, the location and nature of the organellar targeting information contained within OsPHR are unknown. Here, the nuclear and mitochondrial targeting signal sequences of OsPHR were identified by systematic deletion analysis. The nuclear and mitochondrial targeting sequences are harbored within residues 487-489 and 391-401 in the C-terminal region of OsPHR (506 amino acid residues), respectively. The mitochondrial targeting signal represents a distinct topogenic sequence that differs structurally and functionally from classical N-terminal pre-sequences, and this region, in addition to its role in localization to the mitochondria, is essential for the proper functioning of the CPD photolyase. Furthermore, the mitochondrial targeting sequence, which is characteristic of class-II CPD photolyases, was acquired before the divergence of class-II CPD photolyases in eukaryotes. These results indicate that rice plants have evolved a CPD photolyase that functions in mitochondria to protect cells from the harmful effects of UVB radiation.
authors.affiliation: Department of Environmental Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, 980-8577, Japan.
authors.forename: Sayaka
authors.initials: S
authors.lastname: Takahashi
authors.forename: Mika
authors.initials: M
authors.lastname: Teranishi
authors.forename: Masanori
authors.initials: M
authors.lastname: Izumi
authors.forename: Masaaki
authors.initials: M
authors.lastname: Takahashi
authors.forename: Fumio
authors.initials: F
authors.lastname: Takahashi
authors.forename: Jun
authors.initials: J
authors.lastname: Hidema
mesh_terms: D000595:Amino Acid Sequence; D002736:Chloroplasts / Q000648:ultrastructure; D004249:DNA Damage; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D008928:Mitochondria / Q000648:ultrastructure; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals; D012275:Oryza / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects / Q000648:ultrastructure; D010802:Phylogeny; D030821:Plants, Genetically Modified; D021381:Protein Transport; D011740:Pyrimidine Dimers / Q000378:metabolism; D011993:Recombinant Fusion Proteins; D016415:Sequence Alignment; D017384:Sequence Deletion; D014466:Ultraviolet Rays
chemical_list: D019913:Nuclear Localization Signals; D011740:Pyrimidine Dimers; D011993:Recombinant Fusion Proteins; D004255:Deoxyribodipyrimidine Photo-Lyase
keywords: CPD photolyase; cyclobutane pyrimidine dimer (CPD); eukaryote; mitochondrial targeting signal; nuclear localization signal; rice