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Single-Molecule Fluorescence Using Nucleotide Analogs: A Proof-of-Principle.

ABSTRACT: Fluorescent nucleotide analogues, such as 2-aminopurine (2AP) and pyrrolo-C (PyC), have been extensively used to study nucleic acid local conformational dynamics in bulk experiments. Here we present a proof-of-principle approach using 2AP and PyC fluorescence at the single-molecule level. Our data show that ssDNA, dsDNA, or RNA containing both 2AP and PyC can be monitored using single-molecule fluorescence and a click chemistry immobilization method. We demonstrate that this approach can be used to monitor DNA and RNA in real time. This is the first reported assay using fluorescent nucleotide analogs at the single-molecule level. We anticipate that single 2AP or PyC fluorescence will have numerous applications in studies of DNA and RNA, including protein-induced base-flipping dynamics in protein-nucleic acid complexes.

SUBMITTER: Aleman EA

PROVIDER: S-EPMC3985717 | biostudies-literature | 2014 Mar

REPOSITORIES: biostudies-literature

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Single-Molecule Fluorescence Using Nucleotide Analogs: A Proof-of-Principle.

Alemán Elvin A EA de Silva Chamaree C Patrick Eric M EM Musier-Forsyth Karin K Rueda David D

The journal of physical chemistry letters 20140206 5

Fluorescent nucleotide analogues, such as 2-aminopurine (2AP) and pyrrolo-C (PyC), have been extensively used to study nucleic acid local conformational dynamics in bulk experiments. Here we present a proof-of-principle approach using 2AP and PyC fluorescence at the single-molecule level. Our data show that ssDNA, dsDNA, or RNA containing both 2AP and PyC can be monitored using single-molecule fluorescence and a click chemistry immobilization method. We demonstrate that this approach can be used ...[more]

PMID: 24803990

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Project description:Highly specific and potent inhibitors of dihydroorotate dehydrogenase (DHODH), an essential enzyme of the de novo pyrimidine ribonucleotide synthesis pathway, are in clinical trials for autoimmune diseases, viral infections and cancer. However, because DHODH inhibitors (DHODHi) are immunosuppressants they may reduce the anticancer activity of the immune system. Therefore, there may be a need to improve the therapeutic index of DHODHi in cancer patients. The aim of this study was to find strategies to protect activated T cells from DHODHi and to identify cancer types hypersensitive to these inhibitors. First, we observed that like uridine supplementation, adding cytidine to the culture medium protects T cells from DHODH blockage. Next, we identified tumor types with altered expression of pyrimidine ribonucleotide synthesis enzymes. In this regard, we detected that the expression of cytidine deaminase (CDA), which converts cytidine into uridine, is low in an important proportion of cancer cell lines and consistently low in neuroblastoma samples and in cell lines from neuroblastoma and small cell lung carcinoma. This suggested that in the presence of a DHODHi, an excess of cytidine would be deleterious for low CDA expressing cancer cell lines. We show that this was the case (as could be seen almost immediately after treatment) when cells were cultured with fetal bovine serum but, was significantly less evident when cultures contained human serum. One interesting feature of CDA is that aside from acting intracellularly, it is also present in human plasma/serum. Altogether, experiments using recombinant CDA, human serum, pharmacologic inhibition of CDA and T cell/cancer cell co-cultures suggest that the therapeutic index of DHODHi could be improved by selecting patients with low-CDA expressing cancers in combination with strategies to increase cytidine or the cytidine/uridine ratio in the extracellular environment. Collectively, this proof-of-principle study warrants the discovery of agents to deplete extracellular CDA.

Dataset Information

Single-Molecule Fluorescence Using Nucleotide Analogs: A Proof-of-Principle.

Publications

Single-Molecule Fluorescence Using Nucleotide Analogs: A Proof-of-Principle.

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