Photobiological significance of DNA photolgase/Blue-light photoreceptor family

我们报道了非洲爪蟾（6-4）光裂合酶基因的分离，并表明（6-4）光裂合酶与化学计量的FAD非共价结合，非洲爪蟾（6-4）光裂合酶以高亲和力与带有（6-4）光产物的DNA结合，并在光依赖性反应中修复它。为了阐明（6-4）光裂合酶的修复机制，我们用在单一位置携带光产物的合成DNA底物测定了它的结合和催化性质。（6-4）光解酶以高亲和力（kD = 10_）结合双链DNA中的T[6 - 4]T<-9>，并结合单链DNA中的T[6-4]T和双链和单链DNA中的T[Dewar]T，但亲和力略低（kD = -2 X 10_<-8>）。大部分T[6-4]T（6-4）光解酶复合物非常缓慢地解离（koff = 2.9 × 10 - 4<-5 S-1>）。在350-600 nm区域没有第二发色团的绝对作用光谱与酶的吸收光谱非常匹配。修复的量子产率（f）约为0.11。 ...更多信息 （6-4）光裂合酶的完全还原形式（E-FADH-）具有催化活性。对光活化产物的直接分析表明，（6-4）光裂合酶恢复了原始嘧啶。这些结果表明CPD光解酶和（6-4）光解酶非常相似，但它们的结合性质不同，光是诱导昼夜节律的主要环境信号。光信号可以通过改变相位来引导这些节奏。然而，人们对光信号的感知和转导的分子机制知之甚少。光解酶/隐花色素家族的成员含有黄素腺嘌呤二核苷酸（FAD）作为发色团，并且涉及两种不同的功能，DNA修复和环境光信号的光感受。我们报告的克隆，这个家庭的一个新成员，dcry，从果蝇。北方印迹分析表明该基因在多种组织中表达。. dcry mRNA在成人头部以昼夜节律的方式表达，而这种节律性波动在时钟缺陷的per 0和tim 0突变体中被废除。昼夜节律的表达在持续的黑暗中减弱。dcry基因的过表达改变了果蝇运动活动节律中光诱导的相位延迟。这些结果表明，DCRY是一种昼夜光感受器，其表达受昼夜节律钟基因的调控。少

We report isolation of a Xenopus laevis (6-4)photolyase gene, and show that the (6-4)photolyase binds noncovalently to stoichiometric amounts of FAD.Xenopus (6-4) photolyase binds with high affinity to DNA bearing a (6-4) photoproduct and repairs it in a light-dependent reaction. To clarify its repair mechanism of (6-4) photolyase, we determined its binding and catalytic properties using synthetic DNA substrate which carries a photoproduct at a single location. The (6-4)photolyase binds to T[6-4]T in double stranded DNA with high affinity (kD = 10_<-9>) and to T[6-4]T in single stranded DNA and T[Dewar]T in double- and single-stranded DNA although with slightly lower affinity (k_D = -2 x 10_<-8>). Majority of the T[6-4]T (6-4) photolyase-complex dissociates very slowly (koff = 2.9 x 10_<-5 S-1>). Its absolute action spectrum without a second chromophore in the 350-600 nm region closely matches the absorption spectrum of the enzyme. The quantum yield (f) of repair is approximately 0.11. … More The fully reduced form (E-FADH-) of (6-4)photolyase is catalytically active. Direct analysis of the photoreactivated product showed that (6-4) photolyase restores the original pyrimidines. These findings demonstrate that CPD photolyase and (6-4)photolyase are quite similar, but they are different with regard to the binding properties.Light is the major environmental signal for the entrainment of circadian rhythms. Light signals can entrain these rhythms by shifting their phases. However, little is known about the molecular mechanism for the perception and transduction of the light signal. The members of the photolyase/cryptochrome family contain flavin adenine dinucleotide (FAD) as chromophore and are involved in two diverse functions, DNA repair and photoreception of environmental light signals. We report the cloning of a new member of this family, dcry, from Drosophila. Northern blot analysis shows that this gene is expressed in various tissues. . The dcry mRNA is expressed in a circadian manner in adult heads, while such rhythmic fluctuation is abolished in the clock-defective per0 and tim0 mutants. The circadian expression damps in constant darkness. Over-expression of the dcry gene alters the light-induced phase delay in the locomotor activity rhythms of flies. These results suggest that DCRY is a circadian photoreceptor and its expression is regulated by circadian clock genes.. Less