Putative Blue-Light Photoreceptors from Arabidopsis thaliana and Sinapis alba with a High Degree of Sequence Homology to DNA Photolyase Contain the Two Photolyase Cofactors but Lack DNA Repair Activity

Malhotra, Khushbeer; Batschauer, Alfred; Dawut, Lale; Sancar, Aziz

doi:10.1021/bi00020a037

Cited by 256 publications

(255 citation statements)

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“…Because of the high sequence and structural similarities between photolyase and CRY, it is generally assumed that CRYs have the same two cofactors as well. However, no CRY has been purified to date from its native source and those that have been purified as recombinant proteins contain FAD to varying levels and either trace amounts of MTHF or none at all (Lin et al 1995;Malhotra et al 1995;Özgür and Sancar 2003;Song et al 2007). Hence, formal proof that CRYs contain MTHF, or any other secondary chromophore, is lacking.…”

Section: Structures Of Photolyase and Cryptochromementioning

confidence: 99%

“…No native CRY has been purified to date due to their low abundance; instead, the CRYs have been expressed as recombinant proteins using bacterial, insect, or mammalian cells. CRYs purified in this manner contain little to no MTHF chromophore (Lin et al 1995;Malhotra et al 1995;Hsu et al 1996;. With respect to flavin content, CRYs fall into two groups.…”

Section: Physical Propertiesmentioning

confidence: 99%

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Structure and Function of Animal Cryptochromes

Öztürk

Song²,

Özgür³

et al. 2007

Cold Spring Harbor Symposia on Quantitative Biology

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Cryptochrome (CRY) is a photolyase-like flavoprotein with no DNA-repair activity but with known or presumed blue-light receptor function. Animal CRYs have DNA-binding and autokinase activities, and their flavin cofactor is reduced by photoinduced electron transfer. In Drosophila, CRY is a major circadian photoreceptor, and in mammals, the two CRY proteins are core components of the molecular clock and potential circadian photoreceptors. In mammals, CRYs participate in cell cycle regulation and the cellular response to DNA damage by controlling the expression of some cell cycle genes and by directly interacting with checkpoint proteins. in response to blue light (Koornneef et al. 1980), was isolated and sequenced, it revealed high sequence homology with Escherichia coli photolyase, and hence, it was in retrospect, correctly speculated that HY4 encoded a blue light photoreceptor and not a signal transducer involved in blue light response (Ahmad and Cashmore 1993). Later, this protein was named cryptochrome 1 (Lin et al. 1995, and a second Arabidopsis protein that has high homology with CRY1 identified by genomics was named CRY2 . The role of CRY in Arabidopsis growth (CRY1) and differentiation (CRY2) was well established by 1995 (see Guo et al. 1998). However, as late as 1997, it was thought that CRY had no role in circadian photoreception in plants (Millar and Kay 1997).The first report implicating CRY in the circadian clock of any organism, plant or animal, came about from the study of DNA repair, in particular, the repair of UV damage in humans by photolyase. This issue had been controversial for nearly 25 years when Li et al. (1993) conducted an exhaustive study with a highly specific and sensitive assay, concluding that humans, like all placental mammals, lacked photolyase (Li et al. 1993). However, a 1995 release of a human expressed sequence tag (EST) list contained a "photolyase ortholog" entry (Adams et al. 1995). In light of this finding and the discovery of a photolyase in Drosophila and rattlesnake (Todo et al. 1993Kim et al. 1996) that repairs the minor UV-induced lesion, the (6-4) photoproduct, in contrast to the classic photolyase that repairs cyclobutane pyrimidine dimers (CPDs), the earlier conclusion regarding the lack of photolyase in humans needed reevaluation. This was done by Hsu et al. (1996) who, in addition to the "photolyase ortholog" in public databases, discovered a second human photolyase gene. Human cells expressing both genes and recombinant proteins encoded by both genes were tested for CPD and (6-4) photolyase activities and were found to lack both. Moreover, the proteins encoded by these genes, like most photolyases (Johnson et al. 1988) and Arabidopsis CRY (Lin et al. 1995; Malhorta et al. 1995), contained FAD (flavin-adenine dinucleotide) and a pterin cofactor. Therefore, it was concluded that these proteins were not repair enzymes but that, like Arabidopsis CRYs, they performed non-repair-related blue light functions and were named human CRY1 and 2 (Hsu et al. 1996). In humans ...

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Section: Structures Of Photolyase and Cryptochromementioning

confidence: 99%

Section: Physical Propertiesmentioning

confidence: 99%

Structure and Function of Animal Cryptochromes

Öztürk

Song²,

Özgür³

et al. 2007

Cold Spring Harbor Symposia on Quantitative Biology

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“…As hy4 mutants are primarily deficient in their response to B, we had originally proposed that the second chromophore for CRYl was likely to be a deazaflavin (Ahmad & Cashmore 1993). However, it has been demonstrated that a fusion protein between the 'photolyase' domain of CRYl and maltose-binding protein binds a pterin when expressed in E. coli (Malhotra et al 1995). The precise nature of the CRYl second chromophore in Arabidopsis remains to be detemiined.…”

Section: The Ehromophores Of Crylmentioning

confidence: 99%

The cryptochrome family of photoreceptors

Cashmore

1997

Plant Cell & Environment

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“…Class I DNA-photolyases repair cyclobutane pyrimidine dimers by using light energy in the UV-A/blue region (for review see Sancar, 1994). CRY1 and the SA-PHR1 protein from white mustard (Batschauer, 1993), which is 89% identical with Arabidopsis CRY2, bind the chromophores typically present in photolyases, but have no photolyase activity Malhotra et al, 1995). The hy4 mutant is only affected in some blue light responses (Ahmad and Cashmore, 1993;Ahmad et al, 1995;Bagnall et al, 1996;Koornneef et al, 1980), indicating the presence of further blue light receptors in Arabidopsis.…”

Section: Introductionmentioning

confidence: 99%

Nuclear localization of the Arabidopsis blue light receptor cryptochrome 2

et al. 1999

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SummaryThe cryptochrome blue light photoreceptor family of Arabidopsis thaliana consists of two members, CRY1 and CRY2 (PHH1). CRY2 contains a putative nuclear localization signal (NLS) within its C-terminal region. We examined whether CRY2 is localized in the nucleus and whether the C-terminal region of CRY2 is involved in nuclear targeting. Total cellular and nuclear protein extracts from Arabidopsis were subjected to immunoblot analysis with CRY2-speci®c antibodies. Strong CRY2 signals were obtained in the nuclear fraction. Fusion proteins consisting of the green uorescent protein (GFP) and different fragments of CRY2 were expressed in parsley protoplasts and the localization of the fusion proteins was determined bȳ uorescence and confocal laser scanning microscopy. GFP-fusions containing the entire CRY2 protein or its Cterminal region were found exclusively in the nucleus. We conclude from these results that CRY2 is localized in the nucleus and that nuclear localization is mediated by the C-terminal region of CRY2.

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Putative Blue-Light Photoreceptors from Arabidopsis thaliana and Sinapis alba with a High Degree of Sequence Homology to DNA Photolyase Contain the Two Photolyase Cofactors but Lack DNA Repair Activity

Cited by 256 publications

References 20 publications

Structure and Function of Animal Cryptochromes

Structure and Function of Animal Cryptochromes

The cryptochrome family of photoreceptors

Nuclear localization of the Arabidopsis blue light receptor cryptochrome 2

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