Tanida Hiroaki, Tahara Eiji, Mochizuki Miwa, Yamane Yukiko, Ryoji Masaru
Laboratory of Molecular Biology, Department of Life Sciences, Prefectural University of Hiroshima, Hiroshima, Japan.
FEBS J. 2005 Dec;272(23):6098-108. doi: 10.1111/j.1742-4658.2005.05004.x.
Photolyase is a light-dependent enzyme that repairs pyrimidine dimers in DNA. Two types of photolyases have been found in frog Xenopus laevis, one for repairing cyclobutane pyrimidine dimers (CPD photolyase) and the other for pyrimidine-pyrimidone (6-4)photoproduct [(6-4)photolyase]. However, little is known about the former type of the Xenopus photolyases. To characterize this enzyme and its expression profiles, we isolated the entire coding region of a putative CPD photolyase cDNA by extending an EST (expressed sequence tag) sequence obtained from the Xenopus database. Nucleotide sequence analysis of the cDNA revealed a protein of 557 amino acids with close similarity to CPD photolyase of rat kangaroo. The identity of this cDNA was further established by the molecular mass (65 kDa) and the partial amino acid sequences of the major CPD photolyase that we purified from Xenopus ovaries. The gene of this enzyme is expressed in various tissues of Xenopus. Even internal organs like heart express relatively high levels of mRNA. A much smaller amount was found in skin, although UV damage is thought to occur most frequently in this tissue. Such expression profiles suggest that CPD photolyase may have roles in addition to the photorepair function.
光解酶是一种依赖光的酶，可修复DNA中的嘧啶二聚体。在非洲爪蟾（Xenopus laevis）中发现了两种光解酶，一种用于修复环丁烷嘧啶二聚体（CPD光解酶），另一种用于修复嘧啶 - 嘧啶酮（6 - 4）光产物[（6 - 4）光解酶]。然而，对于非洲爪蟾的前一种光解酶知之甚少。为了表征这种酶及其表达谱，我们通过扩展从非洲爪蟾数据库获得的一个EST（表达序列标签）序列，分离出了一个假定的CPD光解酶cDNA的完整编码区。对该cDNA的核苷酸序列分析揭示了一个由557个氨基酸组成的蛋白质，与大鼠袋鼠的CPD光解酶有密切的相似性。我们从非洲爪蟾卵巢中纯化出的主要CPD光解酶的分子量（65 kDa）和部分氨基酸序列进一步确定了该cDNA的身份。这种酶的基因在非洲爪蟾的各种组织中都有表达。即使是心脏等内部器官也表达相对较高水平的mRNA。在皮肤中发现的量要少得多，尽管紫外线损伤被认为在该组织中最常发生。这样的表达谱表明CPD光解酶可能除了光修复功能外还有其他作用。
