Research: Mechanistic studies of DNA repair enzyme spore photoproduct lyase (SPL)
Endospore-forming bacteria are responsible for a number of serious diseases in humans, including anthrax and botulism. Infectious endospores are extremely resistant to a number of harsh environments. Their unusual tolerance to high-dose UV irradiation arises from the action of spore photoproduct lyase (SPL) - a metalloenzyme that repairs the "spore photoproduct" dithymine DNA lesion. SPL uses a 5'-deoxyadenosyl (5'-dA) radical, formed from reductive cleavage of S-adenosylmethionine (SAM), to initiate lesion repair, but little else is known about its mechanism. The objectives of the project are: (1) To understand the photochemistry of thymine damage. We will employ thymine and its analogs to explore the influence on the reaction rates/yields. (2) To identify critical SPL-substrate interactions. We will evaluate SP repair in different DNA local environments. (3) To reveal the detailed reaction mechanism. We will measure the deuterium isotope effect to shed light on the reaction energy surface, examine reaction reversibility, and probe the radical intermediates with various mechanism-based inhibitors. (4) To understand the radical initiation reaction in SPL. We will determine the redox potential of the unique [Fe4S4] cluster, coupled with key amino acids mutagenesis studies.
My laboratory uses the combination of synthetic chemistry, mass spectrometry, mechanistic enzymology, and immunoassays to understand the formation and repair of various DNA lesions in vitro and in vivo. Specifically, we study DNA photoreactions in solar/UV irradiated skin cells to shed light on the molecular mechanisms behind photolesion-induced skin cancer. We also investigate the chemical properties of DNA lesions with an aim of discovering lesion-specific reactions. Such reactions may enable us to selectively label a DNA lesion and subsequently map its distribution in the genome.
Research Areas: Biological Chemistry/Chemical Biology | Inorganic Chemistry/Bioinorganic Chemistry | Organic Chemistry