Ramshackle (Brwd3) promotes light-induced ubiquitylation of
            <i>Drosophila</i>
            Cryptochrome by DDB1-CUL4-ROC1 E3 ligase complex

Öztürk, Nuri; VanVickle-Chavez, Sarah J.; Akileswaran, Lakshmi; Gelder, Russell N. Van; Sancar, Aziz

doi:10.1073/pnas.1303234110

Cited by 58 publications

(61 citation statements)

References 34 publications

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“…As the activity of CRL4 needs to be tightly controlled during HR repair (43,44), uncontrolled CRL4 activity in IP6K1 knockout MEFs might impede HR repair processes. Apart from mediating DNA-damage response, CRL4 targets numerous substrates important for spermatogenesis (45), histone remodeling (11), tuberous sclerosis (46), and circadian rhythms (47). Although IP6K1 is also implicated in some of these processes (6, 7), whether such actions involve CRL4 regulation has not been determined.…”

Section: Discussionmentioning

confidence: 99%

Inositol hexakisphosphate kinase-1 mediates assembly/disassembly of the CRL4–signalosome complex to regulate DNA repair and cell death

Rao

Khan

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Inositol polyphosphates containing an energetic pyrophosphate bond are formed primarily by a family of three inositol hexakisphosphate (IP6) kinases (IP6K1-3). The Cullin-RING ubiquitin ligases (CRLs) regulate diverse biological processes through substrate ubiquitylation. CRL4, comprising the scaffold Cullin 4A/B, the E2-interacting Roc1/2, and the adaptor protein damage-specific DNA-binding protein 1, is activated by DNA damage. Basal CRL4 activity is inhibited by binding to the COP9 signalosome (CSN). UV radiation and other stressors dissociate the complex, leading to E3 ligase activation, but signaling events that trigger signalosome dissociation from CRL4 have been unclear. In the present study, we show that, under basal conditions, IP6K1 forms a ternary complex with CSN and CRL4 in which IP6K1 and CRL4 are inactive. UV dissociates IP6K1 to generate IP7, which then dissociates CSN-CRL4 to activate CRL4. Thus, IP6K1 is a novel CRL4 subunit that transduces UV signals to mediate disassembly of the CRL4-CSN complex, thereby regulating nucleotide excision repair and cell death. Inositol pyrophosphates containing seven (IP7) or more phosphate groups on a myo-inositol ring are synthesized from inositol hexakisphosphate (IP6) primarily by a family of IP6 kinases that are conserved from yeast to humans and mediate diverse physiologic functions (1, 2). Among the three mammalian IP6K isoforms, IP6K1 and IP6K2 are widely distributed, whereas IP6K3 is expressed primarily in the brain (3). IP6K1 plays a role in diabetes (4), DNA homologous recombination (HR) repair (5), spermatogenesis (6), and chromatin modifications (7).The Cullin-RING ubiquitin ligases (CRLs) control fundamental biological processes by mediating 20% of ubiquitindependent protein turnover (8). These E3 ligases are multiprotein complexes composed of the scaffold Cullins (Cul 1-7), the E2-interacting RING-finger protein Roc1/2, adaptor proteins specific for each Cullin family member, and adaptor-interacting substrate receptors that target substrates for ubiquitylation. CRL4, a DNA-damage-sensing member of this family (9), mediates the degradation of numerous substrates involved in cell cycle regulation (CDT1, p21, p27) as well as cell growth or death (c-Jun, p53) and is aberrantly active in many tumor types (10). The CRL4 complex comprises Cul4A/B and the adaptor protein damagespecific DNA binding protein 1 (DDB1). DDB1 binds to a family of WD40 domain-containing proteins that are substrate receptors (11, 12). The complex of DDB1 and its substrate receptor DDB2 binds directly to UV-damaged DNA to initiate nucleotide excision repair (NER) by ubiquitylating local histones and the NER machinery (9). Loss of DDB activity results in group E xeroderma pigmentosum, whose victims are hypersensitive to UV light. However, it remains unclear how CRL4 is activated by UV.In plants, CRL4 is also regulated by UV. Thus, UV absorption by tryptophan residues in the dimer interface of UV-B Resistance 8 (UVR8) triggers dimer dissociation (13). Monomeric UVR8 binds and seque...

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Section: Discussionmentioning

confidence: 99%

Inositol hexakisphosphate kinase-1 mediates assembly/disassembly of the CRL4–signalosome complex to regulate DNA repair and cell death

Rao

Khan

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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“…These results show that Trp triad mutants of cryptochromes are photochemically active and undergo photoreduction in a cellular context. Therefore, conclusions regarding in vivo photochemical redox state transitions cannot be drawn from analysis of Trp triad mutants in vitro for plant and likely also insect cryptochromes (Song et al, 2007;Oztürk et al, 2008;Li et al, 2011;Ozturk et al, 2011Ozturk et al, , 2013Ozturk et al, , 2014). …”

Section: Discussionmentioning

confidence: 99%

Cellular Metabolites Enhance the Light Sensitivity of Arabidopsis Cryptochrome through Alternate Electron Transfer Pathways

et al. 2014

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Cryptochromes are blue light receptors with multiple signaling roles in plants and animals. Plant cryptochrome (cry1 and cry2) biological activity has been linked to flavin photoreduction via an electron transport chain comprising three evolutionarily conserved tryptophan residues known as the Trp triad. Recently, it has been reported that cry2 Trp triad mutants, which fail to undergo photoreduction in vitro, nonetheless show biological activity in vivo, raising the possibility of alternate signaling pathways. Here, we show that Arabidopsis thaliana cry2 proteins containing Trp triad mutations indeed undergo robust photoreduction in living cultured insect cells. UV/Vis and electron paramagnetic resonance spectroscopy resolves the discrepancy between in vivo and in vitro photochemical activity, as small metabolites, including NADPH, NADH, and ATP, were found to promote cry photoreduction even in mutants lacking the classic Trp triad electron transfer chain. These metabolites facilitate alternate electron transfer pathways and increase light-induced radical pair formation. We conclude that cryptochrome activation is consistent with a mechanism of light-induced electron transfer followed by flavin photoreduction in vivo. We further conclude that in vivo modulation by cellular compounds represents a feature of the cryptochrome signaling mechanism that has important consequences for light responsivity and activation.

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“…In the presence of blue light, dCRY binds to TIM and initiates its degradation through action of the E3 ubiquitin ligase, Jetlag (JET) (18)(19)(20)(21)(22)(23)(24). dCRY itself is also degraded in the presence of light with involvement of another E3 ligase, Ramshackle (BRWD3) (25). dCRY contains a C-terminal extension beyond its photolyase homology domain (PHD) that gates light-induced interactions with JET and TIM (6,24,(26)(27)(28).…”

mentioning

confidence: 99%

Flavin reduction activates Drosophila cryptochrome

Vaidya¹,

Top

Manahan³

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

108

159

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Entrainment of circadian rhythms in higher organisms relies on light-sensing proteins that communicate to cellular oscillators composed of delayed transcriptional feedback loops. The principal photoreceptor of the fly circadian clock, Drosophila cryptochrome (dCRY), contains a C-terminal tail (CTT) helix that binds beside a FAD cofactor and is essential for light signaling. Light reduces the dCRY FAD to an anionic semiquinone (ASQ) radical and increases CTT proteolytic susceptibility but does not lead to CTT chemical modification. Additional changes in proteolytic sensitivity and small-angle X-ray scattering define a conformational response of the protein to light that centers at the CTT but also involves regions remote from the flavin center. Reduction of the flavin is kinetically coupled to CTT rearrangement. Chemical reduction to either the ASQ or the fully reduced hydroquinone state produces the same conformational response as does light. The oscillator protein Timeless (TIM) contains a sequence similar to the CTT; the corresponding peptide binds dCRY in light and protects the flavin from oxidation. However, TIM mutants therein still undergo dCRY-mediated degradation. Thus, photoreduction to the ASQ releases the dCRY CTT and promotes binding to at least one region of TIM. Flavin reduction by either light or cellular reductants may be a general mechanism of CRY activation.redox | photolyase | protein-protein interaction

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Ramshackle (Brwd3) promotes light-induced ubiquitylation of Drosophila Cryptochrome by DDB1-CUL4-ROC1 E3 ligase complex

Cited by 58 publications

References 34 publications

Inositol hexakisphosphate kinase-1 mediates assembly/disassembly of the CRL4–signalosome complex to regulate DNA repair and cell death

Inositol hexakisphosphate kinase-1 mediates assembly/disassembly of the CRL4–signalosome complex to regulate DNA repair and cell death

Cellular Metabolites Enhance the Light Sensitivity of Arabidopsis Cryptochrome through Alternate Electron Transfer Pathways

Flavin reduction activates Drosophila cryptochrome

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