Excised group II introns in yeast mitochondria are lariats and can be formed by self-splicing in vitro

Cell ◽  
1986 ◽  
Vol 44 (2) ◽  
pp. 225-234 ◽  
Author(s):  
R. van der Veen ◽  
A.C. Arnberg ◽  
G. van der Horst ◽  
L. Bonen ◽  
H.F. Tabak ◽  
...  
Keyword(s):  
Group Ii Introns ◽  
Yeast Mitochondria ◽  
Group Ii ◽  
Self Splicing

Group II introns deleted for multiple substructures retain self-splicing activity

1992 ◽  
Vol 12 (5) ◽  
pp. 1950-1958
Author(s):  
J L Koch ◽  
S C Boulanger ◽  
S D Dib-Hajj ◽  
S K Hebbar ◽  
P S Perlman
Keyword(s):  
Binding Site ◽  
Splice Junction ◽  
Group Ii Introns ◽  
Splice Site Selection ◽  
Catalytic Core ◽  
Single Deletion ◽  
Group Ii ◽  
Precursor Rna ◽  
Self Splicing

Group II introns can be folded into highly conserved secondary structures with six major substructures or domains. Domains 1 and 5 are known to play key roles in self-splicing, while the roles of domains 2, 3, 4, and 6 are less clear. A trans assay for domain 5 function has been developed which indicates that domain 5 has a binding site on the precursor RNA that is not predicted from any secondary structure element. In this study, the self-splicing group II intron 5 gamma of the coxI gene of yeast mitochondrial DNA was deleted for various intron domains, singly and in combinations. Those mutant introns were characterized for self-splicing reactions in vitro as a means of locating the domain 5 binding site. A single deletion of domain 2, 3, 4, or 6 does not block in vitro reactions at either splice junction, though the deletion of domain 6 reduces the fidelity of 3' splice site selection somewhat. Even the triple deletion lacking domains 2, 4, and 6 retains some self-splicing activity. The deletion of domains 2, 3, 4, and 6 blocks the reaction at the 3' splice junction but not at the 5' junction. From these results, we conclude that the binding site for domain 5 is within domain 1 and that the complex of 5' exon, domain 1, and domain 5 (plus short connecting sequences) constitutes the essential catalytic core of this intron.

scholarly journals Group II introns deleted for multiple substructures retain self-splicing activity.

1992 ◽  
Vol 12 (5) ◽  
pp. 1950-1958 ◽  
Author(s):  
J L Koch ◽  
S C Boulanger ◽  
S D Dib-Hajj ◽  
S K Hebbar ◽  
P S Perlman
Keyword(s):  
Binding Site ◽  
Splice Junction ◽  
Group Ii Introns ◽  
Splice Site Selection ◽  
Catalytic Core ◽  
Single Deletion ◽  
Group Ii ◽  
Precursor Rna ◽  
Self Splicing

Group II introns can be folded into highly conserved secondary structures with six major substructures or domains. Domains 1 and 5 are known to play key roles in self-splicing, while the roles of domains 2, 3, 4, and 6 are less clear. A trans assay for domain 5 function has been developed which indicates that domain 5 has a binding site on the precursor RNA that is not predicted from any secondary structure element. In this study, the self-splicing group II intron 5 gamma of the coxI gene of yeast mitochondrial DNA was deleted for various intron domains, singly and in combinations. Those mutant introns were characterized for self-splicing reactions in vitro as a means of locating the domain 5 binding site. A single deletion of domain 2, 3, 4, or 6 does not block in vitro reactions at either splice junction, though the deletion of domain 6 reduces the fidelity of 3' splice site selection somewhat. Even the triple deletion lacking domains 2, 4, and 6 retains some self-splicing activity. The deletion of domains 2, 3, 4, and 6 blocks the reaction at the 3' splice junction but not at the 5' junction. From these results, we conclude that the binding site for domain 5 is within domain 1 and that the complex of 5' exon, domain 1, and domain 5 (plus short connecting sequences) constitutes the essential catalytic core of this intron.

Self‐Splicing Group II Introns

Ribozymes ◽  
2021 ◽  
pp. 143-167
Author(s):  
Isabel Chillón ◽  
Marco Marcia
Keyword(s):  
Group Ii Introns ◽  
Group Ii ◽  
Self Splicing

scholarly journals Methylation of rRNA as a host defense against rampant group II intron retrotransposition

Mobile DNA ◽  
2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Justin M. Waldern ◽  
Dorie Smith ◽  
Carol Lyn Piazza ◽  
E. Jake Bailey ◽  
Nicholas J. Schiraldi ◽  
...  
Keyword(s):  
Insertional Mutagenesis ◽  
Fold Increase ◽  
Group Ii Intron ◽  
In Vivo Experiments ◽  
Cellular Factors ◽  
Group Ii ◽  
Self Splicing ◽  
Native Host

Abstract Background Group II introns are mobile retroelements, capable of invading new sites in DNA. They are self-splicing ribozymes that complex with an intron-encoded protein to form a ribonucleoprotein that targets DNA after splicing. These molecules can invade DNA site-specifically, through a process known as retrohoming, or can invade ectopic sites through retrotransposition. Retrotransposition, in particular, can be strongly influenced by both environmental and cellular factors. Results To investigate host factors that influence retrotransposition, we performed random insertional mutagenesis using the ISS1 transposon to generate a library of over 1000 mutants in Lactococcus lactis, the native host of the Ll.LtrB group II intron. By screening this library, we identified 92 mutants with increased retrotransposition frequencies (RTP-ups). We found that mutations in amino acid transport and metabolism tended to have increased retrotransposition frequencies. We further explored a subset of these RTP-up mutants, the most striking of which is a mutant in the ribosomal RNA methyltransferase rlmH, which exhibited a reproducible 20-fold increase in retrotransposition frequency. In vitro and in vivo experiments revealed that ribosomes in the rlmH mutant were defective in the m3Ψ modification and exhibited reduced binding to the intron RNA. Conclusions Taken together, our results reinforce the importance of the native host organism in regulating group II intron retrotransposition. In particular, the evidence from the rlmH mutant suggests a role for ribosome modification in limiting rampant retrotransposition.

scholarly journals Group II intron domain 5 facilitates a trans-splicing reaction.

1988 ◽  
Vol 8 (6) ◽  
pp. 2361-2366 ◽  
Author(s):  
K A Jarrell ◽  
R C Dietrich ◽  
P S Perlman
Keyword(s):  
Mitochondrial Dna ◽  
Group Ii Intron ◽  
Intron Sequence ◽  
Trans Splicing ◽  
Group Ii ◽  
Self Splicing ◽  
Yeast Mitochondrial Dna ◽  
Domain 4

A self-splicing group II intron of yeast mitochondrial DNA (aI5g) was divided within intron domain 4 to yield two RNAs that trans-spliced in vitro with associated trans-branching of excised intron fragments. Reformation of the domain 4 secondary structure was not necessary for the trans reaction, since domain 4 sequences were shown to be dispensable. Instead, the trans reaction depended on a previously unpredicted interaction between intron domain 5, the most highly conserved region of group II introns, and another region of the RNA. Domain 5 was shown to be essential for cleavage at the 5' splice site. It stimulated that cleavage when supplied as a trans-acting RNA containing only 42 nucleotides of intron sequence. The relevance of our findings to in vivo trans-splicing mechanisms is discussed.

scholarly journals Group II intron as cold sensor for self-preservation and bacterial conjugation

2020 ◽  
Vol 48 (11) ◽  
pp. 6198-6209 ◽  
Author(s):  
Xiaolong Dong ◽  
Guosheng Qu ◽  
Carol Lyn Piazza ◽  
Marlene Belfort
Keyword(s):  
Group Ii Intron ◽  
Cold Sensitivity ◽  
Group Ii Introns ◽  
Intron Splicing ◽  
Kinetic Trap ◽  
Group Ii ◽  
Self Splicing ◽  
Mrna Targeting ◽  
Cold Sensor

Abstract Group II introns are self-splicing ribozymes and mobile genetic elements. Splicing is required for both expression of the interrupted host gene and intron retromobility. For the pRS01 plasmid-encoded Lactococcus lactis group II intron, Ll.LtrB, splicing enables expression of the intron's host relaxase protein. Relaxase, in turn, initiates horizontal transfer of the conjugative pRS01 plasmid and stimulates retrotransposition of the intron. Little is known about how splicing of bacterial group II introns is influenced by environmental conditions. Here, we show that low temperatures can inhibit Ll.LtrB intron splicing. Whereas autocatalysis is abolished in the cold, splicing is partially restored by the intron-encoded protein (IEP). Structure profiling reveals cold-induced disruptions of key tertiary interactions, suggesting that a kinetic trap prevents the intron RNA from assuming its native state. Interestingly, while reduced levels of transcription and splicing lead to a paucity of excised intron in the cold, levels of relaxase mRNA are maintained, partially due to diminished intron-mediated mRNA targeting, allowing intron spread by conjugal transfer. Taken together, this study demonstrates not only the intrinsic cold sensitivity of group II intron splicing and the role of the IEP for cold-stress adaptation, but also maintenance of horizontal plasmid and intron transfer under cold-shock.

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