On May 14^st, 2019, Small self-cleaving ribozymes catalyze site-specific cleavage of their own phosphodiester backbone with implications for viralgenome replication, pre-mRNA processing and alternative splicing.We report on the 2.1 Å crystal structure of the hatchet ribozymeproduct, which adopts a compact pseudo-symmetric dimeric scaffold, with each monomer stabilized by long-range interactionsinvolving highly conserved nucleotides brought into close proximityof the scissile phosphate. Strikingly, the catalytic pocket contains a cavity capable of accommodating both the modeled scissile phosphate and its flanking 5′ nucleoside. The resulting modeled pre-catalytic conformation incorporates a splayed-apart alignment at the scissile phosphate, thereby providing structurebased insights into the in-line cleavage mechanism. We identifya guanine lining the catalytic pocket positioned to contribute tocleavage chemistry. The functional relevance of structure-basedinsights into hatchet ribozyme catalysis is strongly supported bycleavage assays monitoring the impact of selected nucleobase and atom-specific mutations on ribozyme activity.

Structure of the hatchet ribozyme and the modeling of the cleavage site

Links:https://www.pnas.org/content/early/2019/05/13/1902413116