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

RNA Biology ◽  
2006 ◽  
Vol 3 (4) ◽  
pp. 157-162 ◽  
Author(s):  
Steinar D. Johansen ◽  
Anna Vader ◽  
Eva Sjøttem ◽  
Henrik Nielsen
Keyword(s):  
Ribosomal Dna ◽  
Group I Intron ◽  
Antisense Strand ◽  
Group I ◽  
In Vivo Expression

scholarly journals Sequence specificity of in vivo reverse splicing of the Tetrahymena group I intron

RNA ◽  
1999 ◽  
Vol 5 (1) ◽  
pp. 1-13 ◽  
Author(s):  
JUDIBELLE ROMAN ◽  
MARY NYTHEL RUBIN ◽  
SARAH A. WOODSON
Keyword(s):  
Group I Intron ◽  
Sequence Specificity ◽  
Group I

scholarly journals A Self-Splicing Group I Intron in DNA Polymerase Genes of T7-Like Bacteriophages

2004 ◽  
Vol 186 (23) ◽  
pp. 8153-8155 ◽  
Author(s):  
Richard P. Bonocora ◽  
David A. Shub
Keyword(s):  
Dna Polymerase ◽  
Group I Intron ◽  
Group I Introns ◽  
Homing Endonucleases ◽  
Structural Element ◽  
Group I ◽  
Close Relatives ◽  
Self Splicing

ABSTRACT Group I introns are inserted into genes of a wide variety of bacteriophages of gram-positive bacteria. However, among the phages of enteric and other gram-negative proteobacteria, introns have been encountered only in phage T4 and several of its close relatives. Here we report the insertion of a self-splicing group I intron in the coding sequence of the DNA polymerase genes of ΦI and W31, phages that are closely related to T7. The introns belong to subgroup IA2 and both contain an open reading frame, inserted into structural element P6a, encoding a protein belonging to the HNH family of homing endonucleases. The introns splice efficiently in vivo and self-splice in vitro under mild conditions of ionic strength and temperature. We conclude that there is no barrier for maintenance of group I introns in phages of proteobacteria.

scholarly journals An Unspliced Group I Intron in 23S rRNA LinksChlamydiales, Chloroplasts, and Mitochondria

1999 ◽  
Vol 181 (16) ◽  
pp. 4734-4740 ◽  
Author(s):  
Karin D. E. Everett ◽  
Simona Kahane ◽  
Robin M. Bush ◽  
Maureen G. Friedman
Keyword(s):  
Ribosomal Subunit ◽  
Group I Intron ◽  
23S Rrna ◽  
Rt Pcr ◽  
Naturally Occurring ◽  
Group I ◽  
Ribosomal Function ◽  
Simkania Negevensis

ABSTRACT Chlamydia was the only genus in the orderChlamydiales until the recent characterization ofSimkania negevensis ZT and Parachlamydia acanthamoebae strains. The present study ofChlamydiales 23S ribosomal DNA (rDNA) focuses on a naturally occurring group I intron in the I-CpaI target site of 23S rDNA from S. negevensis. The intron, SnLSU · 1, belonged to the IB4 structural subgroup and was most closely related to large ribosomal subunit introns that express single-motif, LAGLIDADG endonucleases in chloroplasts of algae and in mitochondria of amoebae. RT-PCR and electrophoresis of in vivo rRNA indicated that the intron was not spliced out of the 23S rRNA. The unspliced 658-nt intron is the first group I intron to be found in bacterial rDNA or rRNA, and it may delay the S. negevensis developmental replication cycle by affecting ribosomal function.

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.

In vivo mobility of a group I twintron in nuclear ribosomal DNA of the myxomycete Didymium iridis

1997 ◽  
Vol 24 (4) ◽  
pp. 737-745 ◽  
Author(s):  
Steinar Johansen ◽  
Morten Elde ◽  
Anna Vader ◽  
Peik Haugen ◽  
Kari Haugli ◽  
...  
Keyword(s):  
Ribosomal Dna ◽  
Nuclear Ribosomal Dna ◽  
Group I ◽  
Didymium Iridis

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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