554-01-8Relevant articles and documents
Preparation of carbocyclic phosphonate nucleosides
Jaehne, Gerhard,Mueller, Armin,Kroha, Herbert,Roesner, Manfred,Holzhaeuser, Otto,Meichsner, Christoph,Helsberg, Matthias,Winkler, Irvin,Riess, Guenther
, p. 5335 - 5338 (1992)
A versatile and high-yielding synthesis of racemic carbocyclic phosphonate nucleosides of adenine, hypoxanthine, guanine, cytosine, uracil, and thymine has been developed. These newly prepared compounds are isosteric (and isoelectronic) with (carbo)cyclic 2′,3′-dideoxy- and 2′,3′-dideoxy-2′,3′-didehydronucleoside monophosphates.
Excision of 5-Carboxylcytosine by Thymine DNA Glycosylase
Pidugu, Lakshmi S.,Dai, Qing,Malik, Shuja S.,Pozharski, Edwin,Drohat, Alexander C.
, p. 18851 - 18861 (2019/12/11)
5-Methylcytosine (mC) is an epigenetic mark that is written by methyltransferases, erased through passive and active mechanisms, and impacts transcription, development, diseases including cancer, and aging. Active DNA demethylation involves TET-mediated stepwise oxidation of mC to 5-hydroxymethylcytosine, 5-formylcytosine (fC), or 5-carboxylcytosine (caC), excision of fC or caC by thymine DNA glycosylase (TDG), and subsequent base excision repair. Many elements of this essential process are poorly defined, including TDG excision of caC. To address this problem, we solved high-resolution structures of human TDG bound to DNA with cadC (5-carboxyl-2′-deoxycytidine) flipped into its active site. The structures unveil detailed enzyme-substrate interactions that mediate recognition and removal of caC, many involving water molecules. Importantly, two water molecules contact a carboxylate oxygen of caC and are poised to facilitate acid-catalyzed caC excision. Moreover, a substrate-dependent conformational change in TDG modulates the hydrogen bond interactions for one of these waters, enabling productive interaction with caC. An Asn residue (N191) that is critical for caC excision is found to contact N3 and N4 of caC, suggesting a mechanism for acid-catalyzed base excision that features an N3-protonated form of caC but would be ineffective for C, mC, or hmC. We also investigated another Asn residue (N140) that is catalytically essential and strictly conserved in the TDG-MUG enzyme family. A structure of N140A-TDG bound to cadC DNA provides the first high-resolution insight into how enzyme-substrate interactions, including water molecules, are impacted by depleting the conserved Asn, informing its role in binding and addition of the nucleophilic water molecule.
2′-O-aminoethyl oligoribonucleotides containing novel base analogues: Synthesis and triple-helix formation at pyrimidine/purine inversion sites
Buchini, Sabrina,Leumann, Christian J.
, p. 3152 - 3168 (2007/10/03)
The synthesis of a common sugar intermediate for the 2′-aminoethyl- ribonucleoside synthesis in 9 steps and an overall yield of 33 % starting from D-ribose is described. This intermediate was successfully used for the synthesis of the 2′-aminoethyl-ribonucleosides containing the bases thymine (t), 5-methylcytosine (c), 5-methyl-2-pyrimidinone (x), 2-aminopurine (ap) and guanine (g). These were subsequently transformed into the corresponding cyanoethyl phosphoramidite building blocks for oligonucleotide synthesis. 2′-Aminoethyl oligonucleotide 15-mers were prepared with a DNA synthesizer, and an optimized post-synthetic deprotection protocol has been developed which prevents cyanoethylation of the 2′-amino side chains during conventional ammonia deprotection. A series of fully modified, triplex forming 2′-aminoethyl oligoribonucleotides (2′AE-TFOs) were prepared in which x was designed to bind to CG inversion sites and ap as well as g to TA inversion sites on a double-helical DNA target. The affinity of x-CG base-triple formation in different sequence contexts was assessed by UV- and CD melting analysis. It was found that TFO 15-mers containing up to 5 x residues still form stable triplexes even in the case where all x residues are consecutively arranged in the TFO. The nearest neighbor properties of x have been probed and it was found that triplex stability decreases in the local sequence order -txt- > -txc- ? -cxc-. TFOs containing ap and g were found to bind to their DNA targets with TA inversion sites with less affinity and less selectivity compared to TFOs containing the corresponding deoxyribonucleosides, irrespective whether they were incorporated in TFOs with a DNA or a 2′-AE-RNA backbone. The obtained data suggest that guanine-TA or aminopurine-TA base-triple formation is strongly sensitive to TFO conformation and more efficient in TFOs with a DNA than an RNA backbone. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
