Ultraviolet light (UV)-induced DNA damage can be repaired by DNA photolyase in a light-dependent manner. Two types of photolyase are known, one specific for cyclobutane pyrimidine dimers (CPD photolyase) and another specific for pyrimidine (6-4) pyrimidone photoproducts[(6-4)photolyase]. In contrast to the CPD photolyase, which has been detected in a wide variety of organisms, the (6-4)photolyase has been found only in Drosophila melanogaster. In the present study a gene encoding the Drosophila(6-4)photolyase ws cloned, and the deduced amino acid sequence of the product was found to be similar to the CPD photolyase and to the blue-light photoreceptor of plants. A homolog of the Drosophila (6-4)photolyase gene was also cloned from human cells.
"Although more studies are required to discover species-specific roles of PRMT5, we expect that our observations may have resulted from the different structures of CRYs, since the amino acid composition and length of the C-terminal region of mammalian CRY are quite different from that of Arabidopsis and Drosophila CRY , . In addition, some species-specific mechanisms of circadian clock regulation by CRY have been previously suggested . "
[Show abstract][Hide abstract] ABSTRACT: Circadian clocks are the endogenous oscillators that regulate rhythmic physiological and behavioral changes to correspond to daily light-dark cycles. Molecular dissections have revealed that transcriptional feedback loops of the circadian clock genes drive the molecular oscillation, in which PER/CRY complexes inhibit the transcriptional activity of the CLOCK/BMAL1 heterodimer to constitute a negative feedback loop. In this study, we identified the type II protein arginine methyltransferase 5 (PRMT5) as an interacting molecule of CRY1. Although the Prmt5 gene was constitutively expressed, increased interaction of PRMT5 with CRY1 was observed when the Per1 gene was repressed both in synchronized mouse liver and NIH3T3 cells. Moreover, rhythmic recruitment of PRMT5 and CRY1 to the Per1 gene promoter was found to be associated with an increased level of histone H4R3 dimethylation and Per1 gene repression. Consistently, decreased histone H4R3 dimethylation and altered rhythmic Per1 gene expression were observed in Prmt5-depleted cells. Taken together, these findings provide an insight into the link between histone arginine methylation by PRMT5 and transcriptional regulation of the circadian Per1 gene.
PLoS ONE 10/2012; 7(10):e48152. DOI:10.1371/journal.pone.0048152 · 3.23 Impact Factor
"CRY proteins are highly related to (6–4) photolyases, enzymes repairing UV-induced DNA damage with photon energy , , and contain FAD chromophore , . The photosensory properties of cryptochromes (CRYs) have been investigated in a plant Arabidopsis thaliana and a fruit fly Drosophila melanogaster, and they are shown to play important roles in photomorphogenesis and circadian photoreception, respectively , , . "
[Show abstract][Hide abstract] ABSTRACT: Lunar cycle-associated physiology has been found in a wide variety of organisms. Recent study has revealed that mRNA levels of Cryptochrome (Cry), one of the circadian clock genes, were significantly higher on a full moon night than on a new moon night in coral, implying the involvement of a photoreception system in the lunar-synchronized spawning. To better establish the generalities surrounding such a mechanism and explore the underlying molecular mechanism, we focused on the relationship between lunar phase, Cry gene expression, and the spawning behavior in a lunar-synchronized spawner, the goldlined spinefoot (Siganus guttatus), and we identified two kinds of Cry genes in this animal. Their mRNA levels showed lunar cycle-dependent expression in the medial part of the brain (mesencephalon and diencephalon) peaking at the first quarter moon. Since this lunar phase coincided with the reproductive phase of the goldlined spinefoot, Cry gene expression was considered a state variable in the lunar phase recognition system. Based on the expression profiles of SgCrys together with the moonlight's pattern of timing and duration during its nightly lunar cycle, we have further speculated on a model of lunar phase recognition for reproductive control in the goldlined spinefoot, which integrates both moonlight and circadian signals in a manner similar to photoperiodic response.
PLoS ONE 12/2011; 6(12):e28643. DOI:10.1371/journal.pone.0028643 · 3.23 Impact Factor
"CPD photolyases have been classified into Class I (microbial) and Class II (higher eukaryotes excluding placental mammals) groups, respectively. The 6–4 photolyases from Drosophila and Arabidopsis have strong sequence similarity to class I CPD photolyases (Nakajima et al., 1998; Todo et al., 1996). Similarly cryptochromes, the plant blue light photoreceptors, are 30% similar to the class I microbial photolyases, but demonstrate no photolyase activity (Ahmad & Cashmore, 1993). "
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