Phosphate-modified analogues of m7GTP and m7Gppppm7G—Synthesis and biochemical properties

Abstract

The synthesis and biochemical properties of 17 new mRNA cap analogues are reported. Six of these nucleotides are m7GTP derivatives, whereas 11 are ‘two headed’ tetraphosphate dinucleotides based on a m7Gppppm7G structure. The compounds contain either a boranophosphate or phosphorothioate moiety in the nucleoside neighbouring position(s) and some of them possess an additional methylene group between β and γ phosphorus atoms. The compounds were prepared by divalent metal chloride-mediated coupling of an appropriate m7GMP analogue with a given P1,P2-di(1-imidazolyl) derivative. The analogues were evaluated as tools for studying cap-dependent processes in a number of biochemical assays, including determination of affinity to eukaryotic initiation factor eIF4E, susceptibility to enzymatic hydrolysis, and translational efficiency in vitro. The results indicate that modification in the phosphate chain can increase binding to cap-interacting proteins and provides higher resistance to degradation. Furthermore, modified derivatives of m7GTP were found to be potent inhibitors of cap-dependent translation in cell free systems.