@Article{IPB-1853,
author = {Carbonell, A. and De la Peña, M. and Flores, R. and Gago, S.},
title = {{Effects of the trinucleotide preceding the self-cleavage site on eggplant latent viroid hammerheads: differences in co- and post-transcriptional self-cleavage may explain the lack of trinucleotide AUC in most natural hammerheads}},
year = {2006},
pages = {5613-5622},
journal = {Nucleic Acids Res.},
doi = {10.1093/nar/gkl717},
volume = {34},
abstract = {Eggplant latent viroid (ELVd) can form stable hammerhead structures in its (\+) and (−) strands. These ribozymes have the longest helices I reported in natural hammerheads, with that of the ELVd (\+) hammerhead being particularly stable (5/7 bp are G-C). Moreover, the trinucleotide preceding the self-cleavage site of this hammerhead is AUA, which together with GUA also found in some natural hammerheads, deviate from the GUC present in most natural hammerheads including the ELVd (−) hammerhead. When the AUA trinucleotide preceding the self-cleavage site of the ELVd (\+) hammerhead was substituted by GUA and GUC, as well as by AUC (essentially absent in natural hammerheads), the values of the self-cleavage rate constants at low magnesium of the purified hammerheads were: ELVd-(\+)-AUC≈ELVd-(\+)-GUC\>ELVd-(\+)-GUA\> ELVd-(\+)-AUA. However, the ELVd-(\+)-AUC hammerhead was the catalytically less efficient during in vitro transcription, most likely because of the transient adoption of catalytically-inactive metastable structures. These results suggest that natural hammerheads have been evolutionary selected to function co-transcriptionally, and provide a model explaining the lack of trinucleotide AUC preceding the self-cleavage site of most natural hammerheads. Comparisons with other natural hammerheads showed that the ELVd-(\+)-GUC and ELVd-(\+)-AUC hammerheads are the catalytically most active in a post-transcriptional context with low magnesium.}    
}