Phosphodiester bond

About: Phosphodiester bond is a research topic. Over the lifetime, 2681 publications have been published within this topic receiving 107355 citations.

Adriamycin-induced DNA damage mediated by mammalian DNA topoisomerase II

Abstract: Adriamycin (doxorubicin), a potent antitumor drug in clinical use, interacts with nucleic acids and cell membranes, but the molecular basis for its antitumor activity is unknown. Similar to a number of intercalative antitumor drugs and nonintercalative epipodophyllotoxins (VP-16 and VM-26), adriamycin has been shown to induce single- and double-strand breaks in DNA. These strand breaks are unusual because a covalently bound protein appears to be associated with each broken phosphodiester bond. In studies in vitro, mammalian DNA topoisomerase II mediates DNA damage by adriamycin and other related antitumor drugs.

cGAS produces a 2′-5′-linked cyclic dinucleotide second messenger that activates STING

Abstract: Detection of cytoplasmic DNA represents one of the most fundamental mechanisms of the innate immune system to sense the presence of microbial pathogens. Moreover, erroneous detection of endogenous DNA by the same sensing mechanisms has an important pathophysiological role in certain sterile inflammatory conditions. The endoplasmic-reticulum-resident protein STING is critically required for the initiation of type I interferon signalling upon detection of cytosolic DNA of both exogenous and endogenous origin. Next to its pivotal role in DNA sensing, STING also serves as a direct receptor for the detection of cyclic dinucleotides, which function as second messenger molecules in bacteria. DNA recognition, however, is triggered in an indirect fashion that depends on a recently characterized cytoplasmic nucleotidyl transferase, termed cGAMP synthase (cGAS), which upon interaction with DNA synthesizes a dinucleotide molecule that in turn binds to and activates STING. We here show in vivo and in vitro that the cGAS-catalysed reaction product is distinct from previously characterized cyclic dinucleotides. Using a combinatorial approach based on mass spectrometry, enzymatic digestion, NMR analysis and chemical synthesis we demonstrate that cGAS produces a cyclic GMP-AMP dinucleotide, which comprises a 2'-5' and a 3'-5' phosphodiester linkage >Gp(2'-5')Ap(3'-5')>. We found that the presence of this 2'-5' linkage was required to exert potent activation of human STING. Moreover, we show that cGAS first catalyses the synthesis of a linear 2'-5'-linked dinucleotide, which is then subject to cGAS-dependent cyclization in a second step through a 3'-5' phosphodiester linkage. This 13-membered ring structure defines a novel class of second messenger molecules, extending the family of 2'-5'-linked antiviral biomolecules.

Mapping adenines, guanines, and pyrimidines in RNA

Abstract: The positions of adenines, guanines, and pyrimidines can be determined by partial nuclease digestion of a terminally labeles RNA molecule. In urea, at elevated temperatures, RNase T1 generates a pattern reflecting cleavage at guanines while RNase U2 cleaves only at adenine. A limited alkaline hydrolysis provides a continuum of fragments derived from breaks at every phosphodiester bond. The reaction products are electrophoretically fractionated by size in adjacent lanes of a polyacrylamide gel. An autoradiograph of the gel displays the sequence up to 100 nucleotides from the end of the molecule, although uracil cannot as yet be distinguished from cytosine. These techniques form the basis of an RNA sequencing method and are demonstrated on yeast 5.8S ribosomal RNA.

Three-dimensional structure of a hammerhead ribozyme

Abstract: The hammerhead ribozyme is a small catalytic RNA motif made up of three base-paired stems and a core of highly conserved, non-complementary nucleotides essential for catalysis. The X-ray crystallographic structure of a hammerhead RNA-DNA ribozyme-inhibitor complex at 2.6 A resolution reveals that the base-paired stems are A-form helices and that the core has two structural domains. The first domain is formed by the sequence 5'-CUGA following stem I and is a sharp turn identical to the uridine turn of transfer RNA, whereas the second is a non-Watson-Crick three-base-pair duplex with a divalent-ion binding site. The phosphodiester backbone of the DNA inhibitor strand is splayed out at the phosphate 5' to the cleavage site. The structure indicates that the ribozyme may destabilize a substrate strand in order to facilitate twisting of the substrate to allow cleavage of the scissile bond.

The ups and downs of nucleic acid duplex stability: Structure-stability studies on chemically-modified DNA:RNA duplexes

Abstract: In an effort to discover novel oligonucleotide modifications for antisense therapeutics, we have prepared oligodeoxyribonucleotides containing more than 200 different modifications and measured their affinities for complementary RNA. These include modifications to the heterocyclic bases, the deoxy-ribose sugar and the phosphodiester linkage. From these results, we have been able to determine structure-activity relationships that correlate hybridization affinity with changes in oligonucleotide structure. Data for oligonucleotides containing modified pyrimidine nucleotides are presented. In general, modifications that resulted in the most stable duplexes contained a heteroatom at the 2'-position of the sugar. Other sugar modifications usually led to diminished hybrid stability. Most backbone modifications that led to improved hybridization restricted backbone mobility and resulted in an A-type sugar pucker for the residue 5'to the modified internucleotide linkage. Among the heterocycles, C-5-substituted pyrimidines stood out as substantially increasing duplex stability.