scholarly journals Three different group I introns in the nuclear large subunit ribosomal DNA of the amoeboflagellate Naegleria

1998 ◽  
Vol 26 (2) ◽  
pp. 456-461 ◽  
Author(s):  
J. F. De Jonckheere ◽  
S. Brown
Keyword(s):  
Ribosomal Dna ◽  
Large Subunit ◽  
Group I Introns ◽  
Group I

scholarly journals Analysis of small and large subunit rDNA introns from several ectomycorrhizal fungi species

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0245714
Author(s):  
Li-hong Chen ◽  
Wei Yan ◽  
Ting Wang ◽  
Yu Wang ◽  
Jian Liu ◽  
...  
Keyword(s):  
18S Rdna ◽  
Large Subunit ◽  
Gc Content ◽  
Nucleotide Sequences ◽  
28S Rdna ◽  
Nuclear Ribosomal Dna ◽  
Rdna Site ◽  
Group I Introns ◽  
Intron Insertion ◽  
Group I

The small (18S) and large (28S) nuclear ribosomal DNA (rDNA) introns have been researched and sequenced in a variety of ectomycorrhizal fungal taxa in this study, it is found that both 18S and 28S rDNA would contain introns and display some degree variation in size, nucleotide sequences and insertion positions within the same fungi species (Meliniomyces). Under investigations among the tested isolates, 18S rDNA has four sites for intron insertions, 28S rDNA has two sites for intron insertions. Both 18S and 28S rDNA introns among the tested isolates belong to group I introns with a set of secondary structure elements designated P1-P10 helics and loops. We found a 12 nt nucleotide sequences TACCACAGGGAT at site 2 in the 3’-end of 28S rDNA, site 2 introns just insert the upstream or the downstream of the12 nt nucleotide sequences. Afters sequence analysis of all 18S and 28S rDNA introns from tested isolates, three high conserved regions around 30 nt nucleotides (conserved 1, conserved 2, conserved 3) and identical nucleotides can be found. Conserved 1, conserved 2 and conserved 3 regions have high GC content, GC percentage is almost more than 60%. From our results, it seems that the more convenient host sites, intron sequences and secondary structures, or isolates for 18S and 28S rDNA intron insertion and deletion, the more popular they are. No matter 18S rDNA introns or 18S rDNA introns among tested isolates, complementary base pairing at the splicing sites in P1-IGS-P10 tertiary helix around 5’-end introns and exons were weak.

A mobile group I intron from Physarum polycephalum can insert itself and induce point mutations in the nuclear ribosomal DNA of saccharomyces cerevisiae

1993 ◽  
Vol 13 (2) ◽  
pp. 1023-1033
Author(s):  
D E Muscarella ◽  
V M Vogt
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Ribosomal Dna ◽  
Physarum Polycephalum ◽  
Point Mutations ◽  
Group I Intron ◽  
Yeast Cells ◽  
Nuclear Ribosomal Dna ◽  
Group I Introns ◽  
Recognition Sequence ◽  
Group I

Pp LSU3 is a mobile group I intron in the extrachromosomal nuclear ribosomal DNA (rDNA) of Physarum polycephalum. As found for other mobile introns, Pp LSU3 encodes a site-specific endonuclease, I-Ppo, which mediates "homing" to unoccupied target sites in Physarum rDNA. The recognition sequence for this enzyme is conserved in all eucaryotic nuclear rDNAs. We have introduced this intron into a heterologous species, Saccharomyces cerevisiae, in which nuclear group I introns have not been detected. The expression of Pp LSU3, under control of the inducible GAL10 promoter, was found to be lethal as a consequence of double-strand breaks in the rDNA. However, surviving colonies that are resistant to the lethal effects of I-Ppo because of alterations in the rDNA at the cleavage site were recovered readily. These survivors are of two classes. The first comprises cells that acquired one of three types of point mutations. The second comprises cells in which Pp LSU3 became inserted into the rDNA. In both cases, each resistant survivor appears to carry the same alterations in all approximately 150 rDNA repeats. When it is embedded in yeast rDNA, Pp LSU3 leads to the synthesis of I-Ppo and appears to be mobile in appropriate genetic crosses. The existence of yeast cells carrying a mobile intron should allow dissection of the steps that allow expression of the highly unusual I-Ppo gene.

scholarly journals Characterization of I-Ppo, an intron-encoded endonuclease that mediates homing of a group I intron in the ribosomal DNA of Physarum polycephalum.

1990 ◽  
Vol 10 (7) ◽  
pp. 3386-3396 ◽  
Author(s):  
D E Muscarella ◽  
E L Ellison ◽  
B M Ruoff ◽  
V M Vogt
Keyword(s):  
Ribosomal Dna ◽  
Physarum Polycephalum ◽  
Nuclear Dna ◽  
Expression System ◽  
Target Sequence ◽  
Group I Introns ◽  
Reading Frame ◽  
Group I

A novel and only recently recognized class of enzymes is composed of the site-specific endonucleases encoded by some group I introns. We have characterized several aspects of I-Ppo, the endonuclease that mediates the mobility of intron 3 in the ribosomal DNA of Physarum polycephalum. This intron is unique among mobile group I introns in that it is located in nuclear DNA. We found that I-Ppo is encoded by an open reading frame in the 5' half of intron 3, upstream of the sequences required for self-splicing of group I introns. Either of two AUG initiation codons could start this reading frame, one near the beginning of the intron and the other in the upstream exon, leading to predicted polypeptides of 138 and 160 amino acid residues. The longer polypeptide was the major form translated in vitro in a reticulocyte extract. From nuclease assays of proteins synthesized in vitro with partially deleted DNAs, we conclude that both polypeptides possess endonuclease activity. We also have expressed I-Ppo in Escherichia coli, using a bacteriophage T7 RNA polymerase expression system. The longer polypeptide also was the predominant form made in this system. It showed enzymatic activity in bacteria in vivo, as demonstrated by the cleavage of a plasmid carrying the target site. Like several other intron-encoded endonucleases, I-Ppo makes a four-base staggered cut in its ribosomal DNA target sequence, very near the site where intron 3 becomes integrated in crosses of intron 3-containing and intron 3-lacking Physarum strains.

scholarly journals The Mitochondrial Genome of the Prasinophyte Prasinoderma coloniale Reveals Two Trans-Spliced Group I Introns in the Large Subunit rRNA Gene

PLoS ONE ◽  
2013 ◽  
Vol 8 (12) ◽  
pp. e84325 ◽  
Author(s):  
Jean-François Pombert ◽  
Christian Otis ◽  
Monique Turmel ◽  
Claude Lemieux
Keyword(s):  
Mitochondrial Genome ◽  
Large Subunit ◽  
Rrna Gene ◽  
Group I Introns ◽  
Group I ◽  
Large Subunit Rrna

scholarly journals A mobile group I intron from Physarum polycephalum can insert itself and induce point mutations in the nuclear ribosomal DNA of saccharomyces cerevisiae.

1993 ◽  
Vol 13 (2) ◽  
pp. 1023-1033 ◽  
Author(s):  
D E Muscarella ◽  
V M Vogt
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Ribosomal Dna ◽  
Physarum Polycephalum ◽  
Point Mutations ◽  
Group I Intron ◽  
Yeast Cells ◽  
Nuclear Ribosomal Dna ◽  
Group I Introns ◽  
Recognition Sequence ◽  
Group I

Pp LSU3 is a mobile group I intron in the extrachromosomal nuclear ribosomal DNA (rDNA) of Physarum polycephalum. As found for other mobile introns, Pp LSU3 encodes a site-specific endonuclease, I-Ppo, which mediates "homing" to unoccupied target sites in Physarum rDNA. The recognition sequence for this enzyme is conserved in all eucaryotic nuclear rDNAs. We have introduced this intron into a heterologous species, Saccharomyces cerevisiae, in which nuclear group I introns have not been detected. The expression of Pp LSU3, under control of the inducible GAL10 promoter, was found to be lethal as a consequence of double-strand breaks in the rDNA. However, surviving colonies that are resistant to the lethal effects of I-Ppo because of alterations in the rDNA at the cleavage site were recovered readily. These survivors are of two classes. The first comprises cells that acquired one of three types of point mutations. The second comprises cells in which Pp LSU3 became inserted into the rDNA. In both cases, each resistant survivor appears to carry the same alterations in all approximately 150 rDNA repeats. When it is embedded in yeast rDNA, Pp LSU3 leads to the synthesis of I-Ppo and appears to be mobile in appropriate genetic crosses. The existence of yeast cells carrying a mobile intron should allow dissection of the steps that allow expression of the highly unusual I-Ppo gene.

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