Photolyase is a photoenzyme that uses the energy of blue light to reverse UV-induced DNA damage in many organisms. Cryptochrome is a recently discovered blue-light photoreceptor that regulates the circadian clock in animals (and plants) and growth and development in plants. Both proteins have similar structural architectures but with totally different functions. We have recently elucidated the repair mechanisms and photocycles of cyclobutane pyrimidine dimer by a class of microbial photolyases (class-I) and of pyrimidine-pyrimidone (6-4) photoproduct by (6-4) photolyases. Several new classes of photolyases have been recently discovered with novel active sites and some new functions have also been lately observed. Thus, the first objective (Aim 1) of the project is to systematically characterize the repair of cyclobutane pyrimidine dimer by all other three classes of photolyases and the new function of Dewar repair by (6-4) photolyases. Such systematic investigations will obtain the molecular understanding of detrimental effects of UV radiation on the biosphere. Cryptochrome has been heavily studied by molecular genetics but the mechanistic investigation and understanding are simply lacking. Even the active (functional) redox state of cofactor flavin in cryptochrome is unknown yet. It is only known that cryptochrome proceeds to conformational changes to trigger downstream signal transduction upon blue-light photoreception. Thus, the second objective (Aim 2) is to systematically investigate the redox state(s) and related photochemistry, determine the active state in vivo in plant and animal cryptochromes, and characterize subsequent conformation dynamics and related interactions with downstream proteins. These investigations will uncover the primary process of initial signal transduction and reveal the reaction mechanism and photocycle of cryptochrome. To achieve these goals, we integrate state-of-the-art laser spectroscopy and biochemistry/molecular biology and follow the entire functional evolution of DNA repair and initial signaling of the complex processes with femtosecond temporal resolution and single-residue spatial resolution. The new knowledge obtained from this work on photolyase and cryptochrome is significant to the DNA repair and biological clock fields and, more importantly, is critical to practical applications of rug design for a series of diseases such as skin cancer and mental disorder.

Public Health Relevance

Blue light is used to repair DNA damage caused by UV irradiation through a photoenzyme (photolyase) and to synchronize the circadian clock in animals or to regulate growth and development in plants via signal transduction by a photoreceptor (cryptochrome). DNA damage could lead to skin cancer and circadian rhythms are related to many mental diseases. Here, we develop a novel method by integrating femtosecond laser spectroscopy and biochemistry/molecular biology to systematically characterize the repair dynamics of damaged DNA by photolyase and the primary signaling process by cryptochrome. The new knowledge from these studies is fundamental to the DNA-repair and signal transduction fields and also significant to a series of potential applications suh as drug design and prevention of skin cancer and mental disorder.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Macromolecular Structure and Function B Study Section (MSFB)
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Smith, Ward
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Ohio State University
Schools of Arts and Sciences
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Zwang, Theodore J; Tse, Edmund C M; Zhong, Dongping et al. (2018) A Compass at Weak Magnetic Fields Using Thymine Dimer Repair. ACS Cent Sci 4:405-412
Zhang, Meng; Wang, Lijuan; Zhong, Dongping (2017) Photolyase: Dynamics and electron-transfer mechanisms of DNA repair. Arch Biochem Biophys 632:158-174
Zhang, Meng; Wang, Lijuan; Zhong, Dongping (2017) Photolyase: Dynamics and Mechanisms of Repair of Sun-Induced DNA Damage. Photochem Photobiol 93:78-92
Zhang, Meng; Wang, Lijuan; Shu, Shi et al. (2016) Bifurcating electron-transfer pathways in DNA photolyases determine the repair quantum yield. Science 354:209-213
Faraji, Shirin; Zhong, Dongping; Dreuw, Andreas (2016) Characterization of the Intermediate in and Identification of the Repair Mechanism of (6-4) Photolesions by Photolyases. Angew Chem Int Ed Engl 55:5175-8
Gao, Jie; Wang, Xu; Zhang, Meng et al. (2015) Trp triad-dependent rapid photoreduction is not required for the function of Arabidopsis CRY1. Proc Natl Acad Sci U S A 112:9135-40
Liu, Zheyun; Wang, Lijuan; Zhong, Dongping (2015) Dynamics and mechanisms of DNA repair by photolyase. Phys Chem Chem Phys 17:11933-49
Guo, Xunmin; Liu, Zheyun; Song, Qinhua et al. (2015) Dynamics and mechanism of UV-damaged DNA repair in indole-thymine dimer adduct: molecular origin of low repair quantum efficiency. J Phys Chem B 119:3446-55
Tan, Chuang; Liu, Zheyun; Li, Jiang et al. (2015) The molecular origin of high DNA-repair efficiency by photolyase. Nat Commun 6:7302
Zhong, Dongping (2015) Electron transfer mechanisms of DNA repair by photolyase. Annu Rev Phys Chem 66:691-715

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