Natural circularly permuted group II introns in bacteria produce RNA circles

Adam Roth,Zasha Weinberg,Koen Vanderschuren,Mitchell H Murdock,Ronald R Breaker

doi:10.1016/j.isci.2021.103431

Adam Roth, Zasha Weinberg + Show 3 more

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https://doi.org/10.1016/j.isci.2021.103431

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Journal: iScience	Publication Date: Nov 13, 2021
Citations: 9	License type: cc-by

Affiliation: Howard Hughes Medical Institute, Yale University

Abstract

SummaryGroup II self-splicing introns are large structured RNAs that remove themselves from transcripts while simultaneously sealing the resulting gaps. Some representatives can subsequently reverse splice into DNA, accounting for their pervasive distribution in bacteria. The catalytically active tertiary structure of each group II intron is assembled from six domains that are arranged in a conserved order. Here, we report structural isomers of group II introns, called CP group II ribozymes, wherein the characteristic order of domains has been altered. Domains five and six, which normally reside at the 3′ end of group II introns, instead occupy the 5′ end to form circularly permuted variants. These unusual group II intron derivatives are catalytically active and generate large linear branched and small circular RNAs, reaction products that are markedly different from those generated by canonical group II introns. The biological role of CP group II ribozymes is currently unknown.

Highlights

Catalytic RNA molecules participate in a great diversity of biological processes, including ribozyme-mediated regulation of gene expression, protein synthesis, and RNA modification (Cech and Steitz, 2014)
SUMMARY Group II self-splicing introns are large structured RNAs that remove themselves from transcripts while simultaneously sealing the resulting gaps
The catalytically active tertiary structure of each group II intron is assembled from six domains that are arranged in a conserved order

Summary

Introduction

Catalytic RNA molecules participate in a great diversity of biological processes, including ribozyme-mediated regulation of gene expression, protein synthesis, and RNA modification (Cech and Steitz, 2014). Despite this spectrum of prominent roles, there are very few large catalytic RNAs known to exist in modern cells, probably because those present in the ancient RNA world (Benner et al, 1989; Robertson and Joyce, 2012) have long ago been driven to extinction by competitive pressure from protein-based enzymes. Some contemporary large ribozymes, such as group I and group II self-splicing introns (Lambowitz and Belfort, 1993), have probably solidified their place in modern metabolism by virtue of their roles as specialized selfish genetic elements. This keeps adverse effects on their host organisms to a minimum while simultaneously providing access to a wider variety of genomic insertion sites

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