An mRNA Is Capped by a 2', 5' Lariat Catalyzed by a Group I-Like Ribozyme

  title={An mRNA Is Capped by a 2', 5' Lariat Catalyzed by a Group I-Like Ribozyme},
  author={Henrik Nielsen and Eric Westhof and Steinar Daae Johansen},
  pages={1584 - 1587}
Twin-ribozyme introns are formed by two ribozymes belonging to the group I family and occur in some ribosomal RNA transcripts. The group I-like ribozyme, GIR1, liberates the 5′ end of a homing endonuclease messenger RNA in the slime mold Didymium iridis. We demonstrate that this cleavage occurs by a transesterification reaction with the joining of the first and the third nucleotide of the messenger by a 2′,5′-phosphodiester linkage. Thus, a group I-like ribozyme catalyzes an RNA branching… 

A conformational switch in the DiGIR1 ribozyme involved in release and folding of the downstream I-DirI mRNA.

The role of HEG P1 in GIR1 branching is reminiscent of that of hairpin P-1 in splicing of the Tetrahymena rRNA group I intron and illustrates a general principle in RNA-directed RNA processing.

A new RNA branching activity: the GIR1 ribozyme.

Speciation of a group I intron into a lariat capping ribozyme

The crystal structures of the precleavage and postcleavage LC ribozymes are described, which suggest that structural features inherited from group I Ribozymes have undergone speciation due to profound changes in molecular selection pressure, ultimately giving rise to an original branching ribozyme family.

cis-Acting 5' hammerhead ribozyme optimization for in vitro transcription of highly structured RNAs.

This work presents a method in which incorporation of a full-length hammerhead ribo enzyme with a specific tertiary interaction prevents alternative folding with the lariat capping GIR1 ribozyme and enables complete cleavage in the course of the transcription.

Molecular characterization of a new member of the lariat capping twin-ribozyme introns

The discovery of a twin-ribozyme intron in a member of Heterolobosea expands the distribution pattern of LC ribozymes and identifies a putative regulatory RNA element (AP2.1) in the Allovahlkampfia LC ribozyme that involves homing endonuclease mRNA coding sequences as an important structural component.

Group I intron ribozymes.

This chapter provides a strategy and protocols for initial characterization of new group I intron ribozymes and associated elements found within group I introns.

Lariat capping as a tool to manipulate the 5' end of individual yeast mRNA species in vivo.

This study has used the lariat capping ribozyme from the myxomycete Didymium to replace the mRNA m7G cap of a single reporter mRNA species with a tiny lariat in which the first and the third nucleotide are joined by a 2', 5' phosphodiester bond, consistent with a key role for the m8G cap in mRNA turnover.

Contributions to the study of the architecture and evolution of ribozymes

The pk-turn, a new RNA motif related to k-turns that allow for the formation of a bend of 60° between stems P16 and P17 from the bacterial RNaseP, is identified.

snRNAs as the catalysts of pre-mRNA splicing.

  • S. Valadkhan
  • Biology, Chemistry
    Current opinion in chemical biology
  • 2005

Use of a Lariat Capping Ribozyme to Study Cap Function In Vivo.

This chapter presents protocols to validate the presence of the lariat cap and measure the efficiency of in vivo cleavage by the Lariat capping ribozyme.



Two group I ribozymes with different functions in a nuclear rDNA intron.

GIR1‐mediated cleavage of the excised intron RNA functions in the generation and expression of the mRNA for the intron‐encoded endonuclease I‐DirI, the first example of a group I ribozyme whose presumptive biological function is hydrolysis.

Naegleria nucleolar introns contain two group I ribozymes with different functions in RNA splicing and processing.

The structural organization and catalytic properties of the large nucleolar group I introns (NaSSU1) of the different Naegleria species are characterized and it is proposed that these twin-ribozyme introns define a distinct category of group I intrusion with a conserved structural organizations and function.

Expression of the Naegleria intron endonuclease is dependent on a functional group I self-cleaving ribozyme.

It is demonstrated that self-cleavage of the excised intron also occurs in vivo in Naegleria gruberi, generating an ORF-containing RNA that possesses a short leader with a sequence element likely to be involved in gene expression.

Group I-like ribozymes with a novel core organization perform obligate sequential hydrolytic cleavages at two processing sites.

A new category of self-splicing group I introns with conserved structural organization and function is found among the eukaryotic microorganisms Didymium and Naegleria and a common RNA secondary structure resembling that of group I splicing-ribozyme is proposed, but with some important differences.

Site-specific reverse splicing of a HEG-containing group I intron in ribosomal RNA

The results suggest that reverse splicing, in addition to the established endonuclease-mediated homing mechanism, potentially accounts for group I intron spread into the homologous sites of different strains and species.

In vivo expression of the nucleolar group I intron‐encoded I‐DirI homing endonuclease involves the removal of a spliceosomal intron

The results imply that DiSSU1 uses a unique combination of intron‐supplied ribozyme activity and adaptation to the general RNA polymerase II pathway of mRNA expression to allow a protein to be produced from the RNA polymerases I‐transcribed rDNA.

Kinetic and secondary structure analysis of Naegleria andersoni GIR1, a group I ribozyme whose putative biological function is site-specific hydrolysis.

With a second-order rate constant of 1 x 10(5) min-1 M-1, the self-cleavage reaction of NanGIR1 is 2 orders of magnitude faster than a similar site-specific hydrolysis reaction of the circular form of the Tetrahymena group I intron.