RT Journal Article
SR Electronic
T1 Witnessing the structural evolution of an RNA enzyme
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2021.06.22.449496
DO 10.1101/2021.06.22.449496
A1 Xavier Portillo
A1 Yu-Ting Huang
A1 Ronald R Breaker
A1 David P Horning
A1 Gerald F Joyce
YR 2021
UL http://biorxiv.org/content/early/2021/06/22/2021.06.22.449496.abstract
AB An RNA polymerase ribozyme that has been the subject of extensive directed evolution efforts has attained the ability to synthesize complex functional RNAs, including a full-length copy of its own evolutionary ancestor. During the course of evolution, the catalytic core of the ribozyme has undergone a major structural rearrangement, resulting in a novel tertiary structural element that lies in close proximity to the active site. Through a combination of site-directed mutagenesis, structural probing, and deep sequencing analysis, the trajectory of evolution was seen to involve the progressive stabilization of the new structure, which provides the basis for improved catalytic activity of the ribozyme. Multiple paths to the new structure were explored by the evolving population, converging upon a common solution. Tertiary structural remodeling of RNA is known to occur in nature, as evidenced by the phylogenetic analysis of extant organisms, but this type of structural innovation had not previously been observed in an experimental setting. Despite prior speculation that the catalytic core of the ribozyme had become trapped in a narrow local fitness optimum, the evolving population has broken through to a new fitness locale, suggesting that further improvement of polymerase activity may be achievable.Competing Interest StatementThe authors have declared no competing interest.