scholarly journals The conserved U.G pair in the 5' splice site duplex of a group I intron is required in the first but not the second step of self-splicing.

1989 ◽  
Vol 9 (9) ◽  
pp. 3657-3666 ◽  
Author(s):  
E T Barfod ◽  
T R Cech
Keyword(s):  
Splice Site ◽  
Group I Intron ◽  
Splice Site Mutation ◽  
Second Step ◽  
Site Mutation ◽  
Catalytic Rate Constant ◽  
Group I ◽  
Normal Site ◽  
Guide Sequence ◽  
Self Splicing

Group I self-splicing introns have a 5' splice site duplex (P1) that contains a single conserved base pair (U.G). The U is the last nucleotide of the 5' exon, and the G is part of the internal guide sequence within the intron. Using site-specific mutagenesis and analysis of the rate and accuracy of splicing of the Tetrahymena thermophila group I intron, we found that both the U and the G of the U.G pair are important for the first step of self-splicing (attack of GTP at the 5' splice site). Mutation of the U to a purine activated cryptic 5' splice sites in which a U.G pair was restored; this result emphasizes the preference for a U.G at the splice site. Nevertheless, some splicing persisted at the normal site after introduction of a purine, suggesting that position within the P1 helix is another determinant of 5' splice site choice. When the U was changed to a C, the accuracy of splicing was not affected, but the Km for GTP was increased by a factor of 15 and the catalytic rate constant was decreased by a factor of 7. Substitution of U.A, U.U, G.G, or A.G for the conserved U.G decreased the rate of splicing by an even greater amount. In contrast, mutation of the conserved G enhanced the second step of splicing, as evidenced by a trans-splicing assay. Furthermore, a free 5' exon ending in A or C instead of the conserved U underwent efficient ligation. Thus, unlike the remainder of the P1 helix, which functions in both the first and second steps of self-splicing, the conserved U.G appears to be important only for the first step.

The conserved U.G pair in the 5' splice site duplex of a group I intron is required in the first but not the second step of self-splicing

1989 ◽  
Vol 9 (9) ◽  
pp. 3657-3666
Author(s):  
E T Barfod ◽  
T R Cech
Keyword(s):  
Splice Site ◽  
Group I Intron ◽  
Splice Site Mutation ◽  
Second Step ◽  
Site Mutation ◽  
Catalytic Rate Constant ◽  
Group I ◽  
Normal Site ◽  
Guide Sequence ◽  
Self Splicing

Group I self-splicing introns have a 5' splice site duplex (P1) that contains a single conserved base pair (U.G). The U is the last nucleotide of the 5' exon, and the G is part of the internal guide sequence within the intron. Using site-specific mutagenesis and analysis of the rate and accuracy of splicing of the Tetrahymena thermophila group I intron, we found that both the U and the G of the U.G pair are important for the first step of self-splicing (attack of GTP at the 5' splice site). Mutation of the U to a purine activated cryptic 5' splice sites in which a U.G pair was restored; this result emphasizes the preference for a U.G at the splice site. Nevertheless, some splicing persisted at the normal site after introduction of a purine, suggesting that position within the P1 helix is another determinant of 5' splice site choice. When the U was changed to a C, the accuracy of splicing was not affected, but the Km for GTP was increased by a factor of 15 and the catalytic rate constant was decreased by a factor of 7. Substitution of U.A, U.U, G.G, or A.G for the conserved U.G decreased the rate of splicing by an even greater amount. In contrast, mutation of the conserved G enhanced the second step of splicing, as evidenced by a trans-splicing assay. Furthermore, a free 5' exon ending in A or C instead of the conserved U underwent efficient ligation. Thus, unlike the remainder of the P1 helix, which functions in both the first and second steps of self-splicing, the conserved U.G appears to be important only for the first step.

Base pairing between the 3' exon and an internal guide sequence increases 3' splice site specificity in the Tetrahymena self-splicing rRNA intron

1990 ◽  
Vol 10 (6) ◽  
pp. 2960-2965
Author(s):  
E R Suh ◽  
R B Waring
Keyword(s):  
Splice Site ◽  
Site Specificity ◽  
Group I Introns ◽  
Base Pairing ◽  
Group I ◽  
Guide Sequence ◽  
Compensatory Mutations ◽  
Self Splicing ◽  
Splice Site Usage ◽  
Selection Of

It has been proposed that recognition of the 3' splice site in many group I introns involves base pairing between the start of the 3' exon and a region of the intron known as the internal guide sequence (R. W. Davies, R. B. Waring, J. Ray, T. A. Brown, and C. Scazzocchio, Nature [London] 300:719-724, 1982). We have examined this hypothesis, using the self-splicing rRNA intron from Tetrahymena thermophila. Mutations in the 3' exon that weaken this proposed pairing increased use of a downstream cryptic 3' splice site. Compensatory mutations in the guide sequence that restore this pairing resulted in even stronger selection of the normal 3' splice site. These changes in 3' splice site usage were more pronounced in the background of a mutation (414A) which resulted in an adenine instead of a guanine being the last base of the intron. These results show that the proposed pairing (P10) plays an important role in ensuring that cryptic 3' splice sites are selected against. Surprisingly, the 414A mutation alone did not result in activation of the cryptic 3' splice site.

scholarly journals Base pairing between the 3' exon and an internal guide sequence increases 3' splice site specificity in the Tetrahymena self-splicing rRNA intron.

1990 ◽  
Vol 10 (6) ◽  
pp. 2960-2965 ◽  
Author(s):  
E R Suh ◽  
R B Waring
Keyword(s):  
Splice Site ◽  
Site Specificity ◽  
Group I Introns ◽  
Base Pairing ◽  
Group I ◽  
Guide Sequence ◽  
Compensatory Mutations ◽  
Self Splicing ◽  
Splice Site Usage ◽  
Selection Of

It has been proposed that recognition of the 3' splice site in many group I introns involves base pairing between the start of the 3' exon and a region of the intron known as the internal guide sequence (R. W. Davies, R. B. Waring, J. Ray, T. A. Brown, and C. Scazzocchio, Nature [London] 300:719-724, 1982). We have examined this hypothesis, using the self-splicing rRNA intron from Tetrahymena thermophila. Mutations in the 3' exon that weaken this proposed pairing increased use of a downstream cryptic 3' splice site. Compensatory mutations in the guide sequence that restore this pairing resulted in even stronger selection of the normal 3' splice site. These changes in 3' splice site usage were more pronounced in the background of a mutation (414A) which resulted in an adenine instead of a guanine being the last base of the intron. These results show that the proposed pairing (P10) plays an important role in ensuring that cryptic 3' splice sites are selected against. Surprisingly, the 414A mutation alone did not result in activation of the cryptic 3' splice site.

scholarly journals CBP2 protein promotes in vitro excision of a yeast mitochondrial group I intron.

1989 ◽  
Vol 9 (12) ◽  
pp. 5424-5433 ◽  
Author(s):  
A Gampel ◽  
M Nishikimi ◽  
A Tzagoloff
Keyword(s):  
Splice Site ◽  
Group I Intron ◽  
Nuclear Gene ◽  
Group I Introns ◽  
Wild Type ◽  
Group I ◽  
Mitochondrial Cytochrome B ◽  
High Concentrations ◽  
Self Splicing

The terminal intron (bI2) of the yeast mitochondrial cytochrome b gene is a group I intron capable of self-splicing in vitro at high concentrations of Mg2+. Excision of bI2 in vivo, however, requires a protein encoded by the nuclear gene CBP2. The CBP2 protein has been partially purified from wild-type yeast mitochondria and shown to promote splicing at physiological concentrations of Mg2+. The self-splicing and protein-dependent splicing reactions utilized a guanosine nucleoside cofactor, the hallmark of group I intron self-splicing reactions. Furthermore, mutations that abolished the autocatalytic activity of bI2 also blocked protein-dependent splicing. These results indicated that protein-dependent excision of bI2 is an RNA-catalyzed process involving the same two-step transesterification mechanism responsible for self-splicing of group I introns. We propose that the CBP2 protein binds to the bI2 precursor, thereby stabilizing the catalytically active structure of the RNA. The same or a similar RNA structure is probably induced by high concentrations of Mg2+ in the absence of protein. Binding of the CBP2 protein to the unspliced precursor was supported by the observation that the protein-dependent reaction was saturable by the wild-type precursor. Protein-dependent splicing was competitively inhibited by excised bI2 and by a splicing-defective precursor with a mutation in the 5' exon near the splice site but not by a splicing-defective precursor with a mutation in the core structure. Binding of the CBP2 protein to the precursor RNA had an effect on the 5' splice site helix, as evidenced by suppression of the interaction of an exogenous dinucleotide with the internal guide sequence.

CBP2 protein promotes in vitro excision of a yeast mitochondrial group I intron

1989 ◽  
Vol 9 (12) ◽  
pp. 5424-5433
Author(s):  
A Gampel ◽  
M Nishikimi ◽  
A Tzagoloff
Keyword(s):  
Splice Site ◽  
Group I Intron ◽  
Nuclear Gene ◽  
Group I Introns ◽  
Wild Type ◽  
Group I ◽  
Mitochondrial Cytochrome B ◽  
High Concentrations ◽  
Self Splicing

The terminal intron (bI2) of the yeast mitochondrial cytochrome b gene is a group I intron capable of self-splicing in vitro at high concentrations of Mg2+. Excision of bI2 in vivo, however, requires a protein encoded by the nuclear gene CBP2. The CBP2 protein has been partially purified from wild-type yeast mitochondria and shown to promote splicing at physiological concentrations of Mg2+. The self-splicing and protein-dependent splicing reactions utilized a guanosine nucleoside cofactor, the hallmark of group I intron self-splicing reactions. Furthermore, mutations that abolished the autocatalytic activity of bI2 also blocked protein-dependent splicing. These results indicated that protein-dependent excision of bI2 is an RNA-catalyzed process involving the same two-step transesterification mechanism responsible for self-splicing of group I introns. We propose that the CBP2 protein binds to the bI2 precursor, thereby stabilizing the catalytically active structure of the RNA. The same or a similar RNA structure is probably induced by high concentrations of Mg2+ in the absence of protein. Binding of the CBP2 protein to the unspliced precursor was supported by the observation that the protein-dependent reaction was saturable by the wild-type precursor. Protein-dependent splicing was competitively inhibited by excised bI2 and by a splicing-defective precursor with a mutation in the 5' exon near the splice site but not by a splicing-defective precursor with a mutation in the core structure. Binding of the CBP2 protein to the precursor RNA had an effect on the 5' splice site helix, as evidenced by suppression of the interaction of an exogenous dinucleotide with the internal guide sequence.

Emery-Dreifuss Muscular Dystrophy Type 1 in a 15-Year-Old Patient Due to a Novel Putative Splice-Site Mutation

2017 ◽  
Vol 48 (S 01) ◽  
pp. S1-S45
Author(s):  
O. Schwartz ◽  
J. Althaus ◽  
B. Fiedler ◽  
K. Heß ◽  
W. Paulus ◽  
...  
Keyword(s):  
Muscular Dystrophy ◽  
Splice Site ◽  
Splice Site Mutation ◽  
Site Mutation

A rare cause of fever of unknown origin: hypohidrotic ectodermal dysplasia with a splice site mutation

2018 ◽  
Vol 70 (5) ◽  
Author(s):  
Melahat M. Oguz ◽  
Meltem Akcaboy ◽  
Asuman Gurkan ◽  
Esma Altinel Acoglu ◽  
Pelin Zorlu ◽  
...  
Keyword(s):  
Splice Site ◽  
Fever Of Unknown Origin ◽  
Ectodermal Dysplasia ◽  
Splice Site Mutation ◽  
Unknown Origin ◽  
Hypohidrotic Ectodermal Dysplasia ◽  
Site Mutation
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