Reverse splicing of a mobile twin-ribozyme group I intron into the natural small subunit rRNA insertion site

2005 ◽  
Vol 33 (3) ◽  
pp. 482-484 ◽  
Author(s):  
Å.B. Birgisdottir ◽  
S.D. Johansen
Keyword(s):  
Horizontal Transfer ◽  
Homing Endonuclease ◽  
Insertion Site ◽  
Group I Intron ◽  
Small Subunit ◽  
Group I Introns ◽  
Small Subunit Rrna ◽  
Homing Endonuclease Gene ◽  
Group I ◽  
Endonuclease Gene

A mobile group I intron containing two ribozyme domains and a homing endonuclease gene (twin-ribozyme intron organization) can integrate by reverse splicing into the small subunit rRNA of bacteria and yeast. The integration is sequence-specific and corresponds to the natural insertion site (homing site) of the intron. The reverse splicing is independent of the homing endonuclease gene, but is dependent on the group I splicing ribozyme domain. The observed distribution of group I introns in nature can be explained by horizontal transfer between natural homing sites by reverse splicing and subsequent spread in populations by endonuclease-dependent homing.

scholarly journals A Functional Homing Endonuclease in the Bacillus anthracis nrdE Group I Intron

2007 ◽  
Vol 189 (14) ◽  
pp. 5293-5301 ◽  
Author(s):  
David Nord ◽  
Eduard Torrents ◽  
Britt-Marie Sjöberg
Keyword(s):  
Bacillus Anthracis ◽  
Homing Endonuclease ◽  
Insertion Site ◽  
Group I Intron ◽  
Coding Region ◽  
Recognition Sequence ◽  
Intron Insertion ◽  
Group I ◽  
Serovar Typhimurium ◽  
Self Splicing

ABSTRACT The essential Bacillus anthracis nrdE gene carries a self-splicing group I intron with a putative homing endonuclease belonging to the GIY-YIG family. Here, we show that the nrdE pre-mRNA is spliced and that the homing endonuclease cleaves an intronless nrdE gene 5 nucleotides (nt) upstream of the intron insertion site, producing 2-nt 3′ extensions. We also show that the sequence required for efficient cleavage spans at least 4 bp upstream and 31 bp downstream of the cleaved coding strand. The position of the recognition sequence in relation to the cleavage position is as expected for a GIY-YIG homing endonuclease. Interestingly, nrdE genes from several other Bacillaceae were also susceptible to cleavage, with those of Bacillus cereus, Staphylococcus epidermidis (nrdE1), B. anthracis, and Bacillus thuringiensis serovar konkukian being better substrates than those of Bacillus subtilis, Bacillus lichenformis, and S. epidermidis (nrdE2). On the other hand, nrdE genes from Lactococcus lactis, Escherichia coli, Salmonella enterica serovar Typhimurium, and Corynebacterium ammoniagenes were not cleaved. Intervening sequences (IVSs) residing in protein-coding genes are often found in enzymes involved in DNA metabolism, and the ribonucleotide reductase nrdE gene is a frequent target for self-splicing IVSs. A comparison of nrdE genes from seven gram-positive low-G+C bacteria, two bacteriophages, and Nocardia farcinica showed five different insertion sites for self-splicing IVSs within the coding region of the nrdE gene.

scholarly journals A Phylogenetic Approach to Structural Variation in Organization of Nuclear Group I Introns and Their Ribozymes

2021 ◽  
Vol 7 (3) ◽  
pp. 43
Author(s):  
Betty M. N. Furulund ◽  
Bård O. Karlsen ◽  
Igor Babiak ◽  
Steinar D. Johansen
Keyword(s):  
Binding Site ◽  
Ribosomal Dna ◽  
Homing Endonuclease ◽  
Direct Repeat ◽  
Small Subunit ◽  
Sequence Motif ◽  
Group I Introns ◽  
Group I ◽  
Eukaryotic Microorganisms ◽  
Nuclear Group

Nuclear group I introns are restricted to the ribosomal DNA locus where they interrupt genes for small subunit and large subunit ribosomal RNAs at conserved sites in some eukaryotic microorganisms. Here, the myxomycete protists are a frequent source of nuclear group I introns due to their unique life strategy and a billion years of separate evolution. The ribosomal DNA of the myxomycete Mucilago crustacea was investigated and found to contain seven group I introns, including a direct repeat-containing intron at insertion site S1389 in the small subunit ribosomal RNA gene. We collected, analyzed, and compared 72 S1389 group IC1 introns representing diverse myxomycete taxa. The consensus secondary structure revealed a conserved ribozyme core, but with surprising sequence variations in the guanosine binding site in segment P7. Some S1389 introns harbored large extension sequences in the peripheral region of segment P9 containing direct repeat arrays. These repeats contained up to 52 copies of a putative internal guide sequence motif. Other S1389 introns harbored homing endonuclease genes in segment P1 encoding His-Cys proteins. Homing endonuclease genes were further interrupted by small spliceosomal introns that have to be removed in order to generate the open reading frames. Phylogenetic analyses of S1389 intron and host gene indicated both vertical and horizontal intron transfer during evolution, and revealed sporadic appearances of direct repeats, homing endonuclease genes, and guanosine binding site variants among the myxomycete taxa.

An optional group I intron between the chloroplast small subunit rRNA genes of Chlamydomonas moewusii and C. eugametos

1989 ◽  
Vol 15 (4) ◽  
pp. 277-282 ◽  
Author(s):  
Vincent Durocher ◽  
Antonin Gauthier ◽  
Guy Bellemare ◽  
Claude Lemieux
Keyword(s):  
Group I Intron ◽  
Small Subunit ◽  
Rrna Genes ◽  
Small Subunit Rrna ◽  
Group I ◽  
Chlamydomonas Moewusii
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