Biochemistry, Biophysics, and Structural Biology Commons^™

A Mechanism Of Glucose Tolerance And Stimulation Of Gh1 Β-Glucosidases, Yang Yang, Xinxin Zhang, Qiang Yin, Wei Fang, Zemin Fang, Xiaotang Wang, Xuecheng Zhang, Yazhong Xiao

Department of Chemistry and Biochemistry

β-Glucosidases are enzymes that hydrolyze β-glycosidic bonds to release non-reducing terminal glucosyl residues from glycosides and oligosaccharides, and thus have significant application potential in industries. However, most β-glucosidases are feedback inhibited by the glucose product, which restricts their application. Remarkably, some β-glucosidases of the glycoside hydrolase (GH) 1 family are tolerant to or even stimulated by glucose. Elucidation of the mechanisms of glucose tolerance and stimulation of the GH1 β-glucosidases will be crucial to improve their application through enzyme engineering. In this study, by comparing the primary and tertiary structures of two GH1 β-glucosidases with distinct glucose dependence, some putative …

Ap Endonuclease 1 Prevents Trinucleotide Repeat Expansion Via A Novel Mechanism During Base Excision Repair, Jill M. Beaver, Yanhao Lai, Meng Xu, Astrid H. Casin, Eduardo E. Laverde, Yuan Liu

Department of Chemistry and Biochemistry

Base excision repair (BER) of an oxidized base within a trinucleotide repeat (TNR) tract can lead to TNR expansions that are associated with over 40 human neurodegenerative diseases. This occurs as a result of DNA secondary structures such as hairpins formed during repair. We have previously shown that BER in a TNR hairpin loop can lead to removal of the hairpin, attenuating or preventing TNR expansions. Here, we further provide the first evidence that AP endonuclease 1 (APE1) prevented TNR expansions via its 3′-5′ exonuclease activity and stimulatory effect on DNA ligation during BER in a hairpin loop. Coordinating with …

Oroxylin A Promotes Pten-Mediated Negative Regulation Of Mdm2 Transcription Via Sirt3-Mediated Deacetylation To Stabilize P53 And Inhibit Glycolysis In Wt-P53 Cancer Cells, Kai Zhao, Yuxin Zhou, Chen Qiao, Ting Ni, Zhiyu Li, Xiaotang Wang, Qinglong Guo, Na Lu, Libin Wei

Department of Chemistry and Biochemistry

Introduction

p53 plays important roles in regulating the metabolic reprogramming of cancer, such as aerobic glycolysis. Oroxylin A is a natural active flavonoid with strong anticancer effects both in vitro and in vivo.

Methods

wt-p53 (MCF-7 and HCT116 cells) cancer cells and p53-null H1299 cancer cells were used. The glucose uptake and lactate production were analyzed using Lactic Acid production Detection kit and the Amplex Red Glucose Assay Kit. Then, the protein levels and RNA levels of p53, mouse double minute 2 (MDM2), and p53-targeted glycolytic enzymes were quantified using Western blotting and quantitative polymerase chain reaction (PCR), respectively. …

Inhibition Of Zn(Ii) Binding Type Ia Topoisomerases By Organomercury Compounds And Hg(Ii), Bokun Cheng, Thirunavukkarasu Annamalai, Shayna Sandhaus, Priyanka Bansod, Yuk-Ching Tse-Dinh

Department of Chemistry and Biochemistry

Type IA topoisomerase activities are essential for resolving DNA topological barriers via an enzyme-mediated transient single strand DNA break. Accumulation of topoisomerase DNA cleavage product can lead to cell death or genomic rearrangement. Many antibacterial and anticancer drugs act as topoisomerase poison inhibitors that form stabilized ternary complexes with the topoisomerase covalent intermediate, so it is desirable to identify such inhibitors for type IA topoisomerases. Here we report that organomercury compounds were identified during a fluorescence based screening of the NIH diversity set of small molecules for topoisomerase inhibitors that can increase the DNA cleavage product of Yersinia pestis topoisomerase …

Modification Of Purine And Pyrimidine Nucleosides By Direct C-H Bond Activation, Yong Liang, Stanislaw F. Wnuk

Department of Chemistry and Biochemistry

Transition metal-catalyzed modifications of the activated heterocyclic bases of nucleosides as well as DNA or RNA fragments employing traditional cross-coupling methods have been well-established in nucleic acid chemistry. This review covers advances in the area of cross-coupling reactions in which nucleosides are functionalized via direct activation of the C8-H bond in purine and the C5-H or C6-H bond in uracil bases. The review focuses on Pd/Cu-catalyzed couplings between unactivated nucleoside bases with aryl halides. It also discusses cross-dehydrogenative arylations and alkenylations as well as other reactions used for modification of nucleoside bases that avoid the use of organometallic precursors and …

A Rapid And Sensitive High-Throughput Screening Method To Identify Compounds Targeting Protein-Nucleic Acids Interactions, Nicole Alonso, Roboan Guillen, Jeremy W. Chambers, Fenfei Leng

Department of Chemistry and Biochemistry

DNA-binding and RNA-binding proteins are usually considered ‘undruggable’ partly due to the lack of an efficient method to identify inhibitors from existing small molecule repositories. Here we report a rapid and sensitive high-throughput screening approach to identify compounds targeting protein– nucleic acids interactions based on protein–DNA or protein–RNA interaction enzyme-linked immunosorbent assays (PDI-ELISA or PRI-ELISA). We validated the PDI-ELISA method using the mammalian highmobility- group protein AT-hook 2 (HMGA2) as the protein of interest and netropsin as the inhibitor of HMGA2–DNA interactions. With this method we successfully identified several inhibitors and an activator for HMGA2–DNA interactions from a collection of …

Selective Reduction Of Cr(Vi) In Chromium, Copper And Arsenic (Cca) Mixed Waste Streams Using Uv/Tio2 Photocatalysis, Shan Zheng, Wenjun Jiang, Mamun Rashid, Yong Cai, Dionysios D. Dionysiou, Kevin E. O'Shea

Department of Chemistry and Biochemistry

The highly toxic Cr(VI) is a critical component in the Chromated Copper Arsenate (CCA) formulations extensively employed as wood preservatives. Remediation of CCA mixed waste and discarded treated wood products is a significant challenge. We demonstrate that UV/TiO2 photocatalysis effectively reduces Cr(VI) to less toxic Cr(III) in the presence of arsenate, As(V), and copper, Cu(II). The rapid conversion of Cr(VI) to Cr(III) during UV/TiO2 photocatalysis occurs over a range of concentrations, solution pH and at different Cr:As:Cu ratios. The reduction follows pseudo-first order kinetics and increases with decreasing solution pH. Saturation of the reaction solution with argon during UV/TiO2 photocatalysis …

A 5', 8-Cyclo-2'-Deoxypurine Lesion Induces Trinucleotide Repeat Deletion Via A Unique Lesion Bypass By Dna Polymerase Β., Meng Xu, Yanhao Lai, Zhongliang Jiang, Michael A. Terzidis, Annalisa Masi, Chryssostomos Chatgilialoglu, Yuan Liu

Department of Chemistry and Biochemistry

5′,8-cyclo-2′-deoxypurines (cdPus) are common forms of oxidized DNA lesions resulting from endogenous and environmental oxidative stress such as ionizing radiation. The lesions can only be repaired by nucleotide excision repair with a low efficiency. This results in their accumulation in the genome that leads to stalling of the replication DNA polymerases and poor lesion bypass by translesion DNA polymerases. Trinucleotide repeats (TNRs) consist of tandem repeats of Gs and As and therefore are hotspots of cdPus. In this study, we provided the first evidence that both (5′R)- and (5′S)-5′,8-cyclo-2′-deoxyadenosine (cdA) in a CAG repeat tract caused CTG repeat deletion exclusively …

Base Excision Repair Of Chemotherapeutically-Induced Alkylated Dna Damage Predominantly Causes Contractions Of Expanded Gaa Repeats Associated With Friedreich's Ataxia, Yanhao Lai, Jill M. Beaver, Karla Lorente, Jonathan Melo, Shyama Ramjagsingh, Irina U. Agoulnik, Zunzhen Zhang, Yuan Liu

Department of Chemistry and Biochemistry

Expansion of GAA·TTC repeats within the first intron of the frataxin gene is the cause of Friedreich's ataxia (FRDA), an autosomal recessive neurodegenerative disorder. However, no effective treatment for the disease has been developed as yet. In this study, we explored a possibility of shortening expanded GAA repeats associated with FRDA through chemotherapeutically-induced DNA base lesions and subsequent base excision repair (BER). We provide the first evidence that alkylated DNA damage induced by temozolomide, a chemotherapeutic DNA damaging agent can induce massive GAA repeat contractions/deletions, but only limited expansions in FRDA patient lymphoblasts. We showed that temozolomide-induced GAA repeat instability …

Base Excision Repair Of Oxidative Dna Damage Coupled With Removal Of A Cag Repeat Hairpin Attenuates Trinucleotide Repeat Expansion, Meng Xu, Yanhao Lai, Justin Torner, Yanbin Zhang, Zunzhen Zhang, Yuan Liu

Department of Chemistry and Biochemistry

Trinucleotide repeat (TNR) expansion is responsible for numerous human neurodegenerative diseases. However, the underlying mechanisms remain unclear. Recent studies have shown that DNA base excision repair (BER) can mediate TNR expansion and deletion by removing base lesions in different locations of a TNR tract, indicating that BER can promote or prevent TNR expansion in a damage location–dependent manner. In this study, we provide the first evidence that the repair of a DNA base lesion located in the loop region of a CAG repeat hairpin can remove the hairpin, attenuating repeat expansion. We found that an 8-oxoguanine located in the loop …