The recent transfer of a homing endonuclease gene

Haugen, Peik; Wikmark, Odd-Gunnar; Vader, Anna; Coucheron, Dag H.; Sjøttem, Eva; Johansen, Steinar

doi:10.1093/nar/gki564

Cited by 27 publications

(36 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The HEG spreads in the population through the cleavage activity of the HEase, and, once all possible homing sites have been invaded, the HEG is no longer under purifying selection pressure and begins to accumulate mutations and degenerate. For noncoding intron sequences, there may be little pressure for sequence conservation and the sequences that flank the HEG may begin to accumulate mutations (Haugen et al 2005). However, if the HEG happens to evolve such that the HEase targets a new site, such as intron-less versions of the host gene, the HEG then benefits the intron by mobilizing it and allowing it to spread in the genome or to be transferred horizontally along with the HEG (Loizos et al 1994;Zeng et al 2009).…”

Section: Speculations On the Origins Of The Group II Ribozyme/lheg Comentioning

confidence: 99%

A group II intron encodes a functional LAGLIDADG homing endonuclease and self-splices under moderate temperature and ionic conditions

Mullineux¹,

Costa²,

Bassi³

et al. 2010

RNA

View full text Add to dashboard Cite

A group II intron encoding a protein belonging to the LAGLIDADG family of homing endonucleases was identified in the mitochondrial rns gene of the filamentous fungus Leptographium truncatum, and the catalytic activities of both the intron and its encoded protein were characterized. A model of the RNA secondary structure indicates that the intron is a member of the IIB1 subclass and the open reading frame is inserted in ribozyme domain III. In vitro assays carried out with two versions of the intron, one in which the open reading frame was removed and the other in which it was present, demonstrate that both versions of the intron readily self-splice at 37°C and at a concentration of MgCl 2 as low as 6 mM. The open reading frame encodes a functional LAGLIDADG homing endonuclease that cleaves 2 (top strand) and 6 (bottom strand) nucleotides (nt) upstream of the intron insertion site, generating 4 nt 39 OH overhangs. In vitro splicing assays carried out in the absence and presence of the intron-encoded protein indicate that the protein does not enhance intron splicing, and RNA-binding assays show that the protein does not appear to bind to the intron RNA precursor transcript. These findings raise intriguing questions concerning the functional and evolutionary relationships of the two components of this unique composite element.

show abstract

Section: Speculations On the Origins Of The Group II Ribozyme/lheg Comentioning

confidence: 99%

A group II intron encodes a functional LAGLIDADG homing endonuclease and self-splices under moderate temperature and ionic conditions

Mullineux¹,

Costa²,

Bassi³

et al. 2010

RNA

View full text Add to dashboard Cite

show abstract

“…8 Finally, the I-PpoI HEG, found within the Ppo.L1925 group I intron in Physarum polycephalum, is transcribed by RNA pol I and translated from an mRNA corresponding to the excised linear group I intron RNA. [9][10][11] Dir.S956-2 is a complex HEG-containing group IC1 intron located within the small subunit (SSU) rDNA of the D. iridis Costa Rica 8 isolate 12 at the exact same location as Dir.S956-1. The HEG is inserted into P8 of the group I intron, but on the opposite www.landesbioscience.com RNA Biologystrand of the one encoding the precursor (pre) rRNA (Fig.…”

Section: Introductionmentioning

confidence: 99%

In vivo Expression of a Group I Intron HEG from the Antisense Strand of Didymium Ribosomal DNA

Johansen¹,

Vader²,

Sjøttem³

et al. 2006

RNA Biology

View full text Add to dashboard Cite

Two different isolates of the myxomycete Didymium iridis harbour homing endonuclease genes that are expressed from group I introns inserted into identical sites within the small subunit ribosomal DNA. The homing endonuclease proteins are related in sequence, and their gene structures share similar features such as the presence of small spliceosomal introns and functional polyadenylation sites. However, they are transcribed from opposite strands of the ribosomal DNA and presumable by different RNA polymerases. We have previously described the in vivo expression of the I-DirI homing endonuclease from within the ribosomal RNA precursor. In this paper, we demonstrate the in vivo expression of the I-DirII homing endonuclease from the opposite strand of the Didymium rRNA gene. A comparison of the expression strategies of the two genes demonstrates the feasibility of antisense expression and provides insight into nucleolar gene expression.

show abstract

“…Twintrons (30), where two distinct group I introns are associated with each other, and IStrons (77,107), where a group I intron and an insertion sequence (IS) are seen together, are two such cases. Rarely, spliceosomal introns are also found within group I introns (48). As seen below, group I introns also associate with endonucleases.…”

Section: Group I Intronsmentioning

confidence: 94%

“…Several studies have shown that HEs and their corresponding introns or inteins have separate phylogenetic histories (36,46). Also, similar inteins and introns were found to contain different types of HEs, and closely related HEs are known to be encoded within distantly related introns (48). Moreover, "freestanding" endonucleases that are mobile, even without being associated with an intron or an intein, have been found abundantly in some bacteriophage genomes (7,101).…”

Section: Disparate Origins Convergent Parasitic Strategiesmentioning

confidence: 99%

“…This stable chimera can now efficiently spread through the population by homing to cognate sites and rarely even to ectopic sites. Alternatively, in some cases an HE might invade an intron due to the presence of a cleavage site within a peripheral loop of the intron (48,71). In this event, the HE must adapt quickly to recognize and cleave intronless alleles of the target gene so as to facilitate homing, which in turn will ensure its maintenance within the intron.…”

Section: Disparate Origins Convergent Parasitic Strategiesmentioning

confidence: 99%

See 1 more Smart Citation

Group I Introns and Inteins: Disparate Origins but Convergent Parasitic Strategies

Raghavan

Minnick

2009

J Bacteriol

View full text Add to dashboard Cite

Genomes of most organisms harbor DNA of foreign origin that has no known function. Since these elements may not contribute to a host's fitness but utilize host resources for their perpetuation, it is appropriate to consider them genetic parasites (4). With the advent of sequencing technologies, a wide variety of parasitic elements have been discovered in bacteria from all environments, including obligate intracellular pathogens (100), which were thought to be shielded from horizontal gene transfer (HGT). Detection of a parasitic genetic element in a genome represents only a snapshot of the continuing and dynamic interplay between the host's attempts to purge the element and the element's ability to persist. These adaptable genetic parasites have evolved mechanisms to overcome defenses (75) of the cellular machinery to ultimately invade, colonize, and replicate within the host. Their success is very evident in the human genome, which consists mostly of such apparently superfluous DNA (65). Even compact bacterial genomes packed with functional genes contain mobile genetic elements (100), underscoring their universality in nature.A number of parasitic genetic elements are found in bacterial genomes, including transposons, insertion sequences, prophages, introns, inteins, and intervening sequences. While bacteria, especially pathogenic bacteria, are well studied, their parasitic genetic elements have not received as much attention. In the past few years, while studying the obligate intracellular pathogen Coxiella burnetii, we came to appreciate the intimate relationship between bacterial hosts and parasitic elements (92,93). In addition, interesting new studies have shed light on the evolutionary histories of group I introns, inteins, and homing endonucleases (HEs) (9, 109) and infused excitement into the field. This minireview, which focuses on the biology and evolution of group I introns and inteins found in bacteria, is an attempt to catalyze interest among bacteriologists in these fascinating genetic parasites. GROUP I INTRONSIntrons are noncoding, intragenic regions that are removed from precursor RNA to form the mature RNA by splicing the exons (coding regions that flank introns) together. They are much more common in eukaryotes than in bacteria (50). Introns are classified into four groups based on splicing mechanisms (47): group I, group II/group III, spliceosomal, and tRNA/archaeal introns. Spliceosomal introns are found in eukaryotes and utilize spliceosomes (large protein-RNA complexes) for splicing (70), whereas tRNA introns splice with the help of specialized enzymes (74). Group I and group II introns are able to self-splice-using different mechanisms-without the aid of any proteins and are thus referred to as ribozymes (104). A self-splicing group I intron from Tetrahymena thermophila was one of the first ribozymes to be described, in the early 1980s (61). Ribozymes are considered legacies of a primordial RNA world, where RNA possessed both informationencoding and catalytic properties, before the adven...

show abstract

The recent transfer of a homing endonuclease gene

Cited by 27 publications

References 28 publications

A group II intron encodes a functional LAGLIDADG homing endonuclease and self-splices under moderate temperature and ionic conditions

A group II intron encodes a functional LAGLIDADG homing endonuclease and self-splices under moderate temperature and ionic conditions

In vivo Expression of a Group I Intron HEG from the Antisense Strand of Didymium Ribosomal DNA

Group I Introns and Inteins: Disparate Origins but Convergent Parasitic Strategies

Contact Info

Product

Resources

About