Alkaline opening of imidazole ring of 7-methylguanosine. 1. Analysis of the resulting pyrimidine derivatives

Abstract

Column chromatography and spectroscopy have been employed in analyzing pyrimidine derivatives obtained from alkaline-treated 7-methylguanosine (7-meGuo). High performance liquid chromatography (HPLC) revealed that the alkaline generated products consist predominantly of two forms of ring opened 7-methylguanine (rom7Gua) in equal amounts. Material from both Dowex 50 and Sephadex LH-20 columns was readily resolvable into two HPLC peaks. The species in one peak appears to be composed of formylated and that in the other of deformylated rom7Gua. The presence of a deformylated species is supported by the absence of radioactivity in one of the two peaks obtained when ring opened [8-14C]-guanosine was analyzed by HPLC. The formylated species was retained on the liquid chromatography column for 8 min with a 3% methanol, 0.01 M NH4H2PO4 (pH 5.1) solvent and for 6 min with a 6% methanol, 0.01 N NH4H2PO4 (pH 5.1) solvent system; the deformylated species was retained for 6.3 min with the first solvent and 4.5 min with the second solvent. Subsequent to Dowex 50 chromatography in an ammonium formate solvent, abut 90% of the material was formylated. When stored at 24 degrees C for 72 h in a solvent without formate ions, the material was shown by HPLC to consist of equal amounts of the formylated and deformylated species. These results indicate that the two species of rom7Gua are in equilibrium. The rom7Gua excised from DNA by formamidopyrimidine (FAPy)-DNA glycosylase was shown to coelute with the formylated species.

Preparation and Properties of mRNA 5-cap Structure

“…the nucleophilic attack on the C8 atom is rapid and results in formation of a complex mixture of intermediates [25,51,52]. The half-life of the disappearance of m 7 Guo is 63 s in 10 mM NaOH at 25 °C [25].…”

AlkAniline‐Seq: Profiling of m7G and m3C RNA Modifications at Single Nucleotide Resolution

“…AlkAniline-Seq combines three successive treatments:i)RNA alkaline hydrolysis,ii) extensive 5'-and 3'dephosphorylation and iii)a niline cleavage ( Figure 1a). According to the literature, [27,28] m 7 Gr esidues are subject of nucleophilic attack by hydroxide anions,ar eaction that ultimately leads to ring opening, base elimination and creation of an abasic site. [29] Upon exposing m 7 Gnucleosides to the alkaline conditions of the AlkAniline-Seq protocol, known intermediates of this decay pathway were indeed detected by LC-MS ( Figure S2bcd), which is consistent with the subsequent formation of abasic sites.…”

The aflatoxin B 1 formamidopyrimidine adduct plays a major role in causing the types of mutations observed in human hepatocellular carcinoma

“…1) based on data obtained for the imidazole ring-opened form of 7-methylguanine. This adduct forms two rotamers, indicating that structural duality may be a common characteristic of formamidopyrimidines (30)(31)(32)(33). Under the conditions by which the AFB 1 -FAPY oligonucleotides are made and stored, an equilibrium exists between the major and minor presumed rotamers at a ratio of 2:1, and these oligonucleotides can be used in studies of mutagenicity.…”