Branchpoint Sugar Stereochemistry Determines the Hydrolytic Susceptibility of Branched RNA Fragments by the Yeast Debranching Enzyme (YDBR)

Abstract A series of branched RNAs (Y-shaped) related to yeast pre-mRNA splicing intermediates were synthesized incorporating both natural (i.e., ribose) and non-natural (i.e., arabinose, xylose and acyclic nucleoside) branchpoints in order to examine the effect of sugar conformation and phosphodiester configuration on yDBR hydrolytic efficiency. The results indicate that 2′-phosphodiester scission with yDBR occurs only with a cis-arrangement of phosphate groups at the branchpoint (i.e., ribose) thereby discriminating between all other configurations.