U1 small nuclear ribonucleoproteins are required early during spliceosome assembly

1987 ◽  
Vol 7 (8) ◽  
pp. 2877-2883
Author(s):  
M Zillmann ◽  
S D Rose ◽  
S M Berget
Keyword(s):  
Gel Electrophoresis ◽  
Early Recognition ◽  
Splice Junction ◽  
Specific Antibodies ◽  
U1 Snrnp ◽  
In Vitro Splicing ◽  
Precursor Rna ◽  
Splice Junctions ◽  
Small Nuclear Ribonucleoproteins

U1 small nuclear ribonucleoproteins (snRNPs) are required for in vitro splicing of pre-mRNA. Sequences within U1 RNA hybridize to, and thus recognize, 5' splice junctions. We have investigated the mechanism of association of U1 snRNPs with the spliceosome. U1-specific antibodies detected U1 association with precursor RNA early during assembly. Removal of the 5' terminal sequences of U1 RNA by oligo-directed cleavage or removal of U1 snRNPs by immunoprecipitation prior to the addition of precursor RNA depressed the association of all snRNPs with precursor RNA as detected by immunoprecipitation of splicing complexes by either Sm or U1-specific antibodies. Assembly of the spliceosome as monitored by gel electrophoresis was also depressed after cleavage of U1 RNA. The dependency of Sm precipitability of precursor RNA upon the presence of U1 snRNPs suggests that U1 snRNPs participate in the early recognition of substrate RNAs by U2 to U6 snRNPs. Although removal of the 5'-terminal sequences of U1 depressed U1 snRNP association with precursor RNA, it did not eliminate it, suggesting semistable association of U1 snRNPs with the assembling spliceosome in the absence of U1 RNA hybridization. This association was not dependent upon 5' splice junction sequences but was dependent upon 3' intronic sequences, indicating that U1 snRNPs interact with factors recognizing 3' intronic sequences. Mutual dependence of 5' and 3' recognition factors suggests significant snRNP-snRNP communication during early assembly.

scholarly journals U1 small nuclear ribonucleoproteins are required early during spliceosome assembly.

1987 ◽  
Vol 7 (8) ◽  
pp. 2877-2883 ◽  
Author(s):  
M Zillmann ◽  
S D Rose ◽  
S M Berget
Keyword(s):  
Gel Electrophoresis ◽  
Early Recognition ◽  
Splice Junction ◽  
Specific Antibodies ◽  
U1 Snrnp ◽  
In Vitro Splicing ◽  
Precursor Rna ◽  
Splice Junctions ◽  
Small Nuclear Ribonucleoproteins

U1 small nuclear ribonucleoproteins (snRNPs) are required for in vitro splicing of pre-mRNA. Sequences within U1 RNA hybridize to, and thus recognize, 5' splice junctions. We have investigated the mechanism of association of U1 snRNPs with the spliceosome. U1-specific antibodies detected U1 association with precursor RNA early during assembly. Removal of the 5' terminal sequences of U1 RNA by oligo-directed cleavage or removal of U1 snRNPs by immunoprecipitation prior to the addition of precursor RNA depressed the association of all snRNPs with precursor RNA as detected by immunoprecipitation of splicing complexes by either Sm or U1-specific antibodies. Assembly of the spliceosome as monitored by gel electrophoresis was also depressed after cleavage of U1 RNA. The dependency of Sm precipitability of precursor RNA upon the presence of U1 snRNPs suggests that U1 snRNPs participate in the early recognition of substrate RNAs by U2 to U6 snRNPs. Although removal of the 5'-terminal sequences of U1 depressed U1 snRNP association with precursor RNA, it did not eliminate it, suggesting semistable association of U1 snRNPs with the assembling spliceosome in the absence of U1 RNA hybridization. This association was not dependent upon 5' splice junction sequences but was dependent upon 3' intronic sequences, indicating that U1 snRNPs interact with factors recognizing 3' intronic sequences. Mutual dependence of 5' and 3' recognition factors suggests significant snRNP-snRNP communication during early assembly.

scholarly journals Gel electrophoretic isolation of splicing complexes containing U1 small nuclear ribonucleoprotein particles.

1988 ◽  
Vol 8 (2) ◽  
pp. 814-821 ◽  
Author(s):  
M Zillmann ◽  
M L Zapp ◽  
S M Berget
Keyword(s):  
Gel Electrophoresis ◽  
Splice Junction ◽  
Rnase H ◽  
Exon 2 ◽  
Small Nuclear Ribonucleoprotein ◽  
Complementary Oligonucleotide ◽  
Exon 1 ◽  
Precursor Rna ◽  
Splice Junctions

Assembly of splicing precursor RNAs into ribonucleoprotein particle (RNP) complexes during incubation in in vitro splicing extracts was monitored by a new system of RNP gel electrophoresis. The temporal pattern of assembly observed by our system was identical to that obtained by other gel and gradient methodologies. In contrast to the results obtained by other systems, however, we observed requirements of U1 small nuclear RNPs (snRNPs) and 5' splice junction sequences for formation of specific complexes and retention of U1 snRNPs within gel-fractionated complexes. Single-intron substrate RNAs rapidly assembled into slow-migrating complexes. The first specific complex (A) appeared within a minute of incubation and required ATP, 5' and 3' precursor RNA consensus sequences, and intact U1 and U2 RNAs for formation. A second complex (B) containing precursor RNA appeared after 15 min of incubation. Lariat-exon 2 and exon 1 intermediates first appeared in this complex, operationally defining it as the active spliceosome. U4 RNA was required for appearance of complex B. Released lariat first appeared in a complex of intermediate mobility (A') and subsequently in rapidly migrating diffuse complexes. Ligated product RNA was observed only in fast-migrating complexes. U1 snRNPs were detected as components of gel-isolated complexes. Radiolabeled RNA within the A and B complexes was immunoprecipitated by U1-specific antibodies under gel-loading conditions and from gel-isolated complexes. Therefore, the RNP antigen remained associated with assembled complexes during gel electrophoresis. In addition, 5' splice junction sequences within gel-isolated A and B complexes were inaccessible to RNase H cleavage in the presence of a complementary oligonucleotide. Therefore, nuclear factors that bind 5' splice junctions also remained associated with 5' splice junctions under our gel conditions.

Gel electrophoretic isolation of splicing complexes containing U1 small nuclear ribonucleoprotein particles

1988 ◽  
Vol 8 (2) ◽  
pp. 814-821
Author(s):  
M Zillmann ◽  
M L Zapp ◽  
S M Berget
Keyword(s):  
Gel Electrophoresis ◽  
Splice Junction ◽  
Rnase H ◽  
Exon 2 ◽  
Small Nuclear Ribonucleoprotein ◽  
Complementary Oligonucleotide ◽  
Exon 1 ◽  
Precursor Rna ◽  
Splice Junctions

Assembly of splicing precursor RNAs into ribonucleoprotein particle (RNP) complexes during incubation in in vitro splicing extracts was monitored by a new system of RNP gel electrophoresis. The temporal pattern of assembly observed by our system was identical to that obtained by other gel and gradient methodologies. In contrast to the results obtained by other systems, however, we observed requirements of U1 small nuclear RNPs (snRNPs) and 5' splice junction sequences for formation of specific complexes and retention of U1 snRNPs within gel-fractionated complexes. Single-intron substrate RNAs rapidly assembled into slow-migrating complexes. The first specific complex (A) appeared within a minute of incubation and required ATP, 5' and 3' precursor RNA consensus sequences, and intact U1 and U2 RNAs for formation. A second complex (B) containing precursor RNA appeared after 15 min of incubation. Lariat-exon 2 and exon 1 intermediates first appeared in this complex, operationally defining it as the active spliceosome. U4 RNA was required for appearance of complex B. Released lariat first appeared in a complex of intermediate mobility (A') and subsequently in rapidly migrating diffuse complexes. Ligated product RNA was observed only in fast-migrating complexes. U1 snRNPs were detected as components of gel-isolated complexes. Radiolabeled RNA within the A and B complexes was immunoprecipitated by U1-specific antibodies under gel-loading conditions and from gel-isolated complexes. Therefore, the RNP antigen remained associated with assembled complexes during gel electrophoresis. In addition, 5' splice junction sequences within gel-isolated A and B complexes were inaccessible to RNase H cleavage in the presence of a complementary oligonucleotide. Therefore, nuclear factors that bind 5' splice junctions also remained associated with 5' splice junctions under our gel conditions.

The splicing factor Prp17 interacts with the U2, U5 and U6 snRNPs and associates with the spliceosome pre- and post-catalysis

2008 ◽  
Vol 416 (3) ◽  
pp. 365-374 ◽  
Author(s):  
Aparna K. Sapra ◽  
Piyush Khandelia ◽  
Usha Vijayraghavan
Keyword(s):  
Second Step ◽  
Splicing Factors ◽  
Temperature Sensitive ◽  
Biochemical Basis ◽  
Association Analyses ◽  
Small Nuclear Rnas ◽  
In Vitro Splicing ◽  
Mechanistic Basis ◽  
Small Nuclear Ribonucleoproteins

Saccharomyces cerevisiae PRP17-null mutants are temperature-sensitive for growth. In vitro splicing with extracts lacking Prp17 are kinetically slow for the first step of splicing and are arrested for the second step at temperatures greater than 34 °C. In the present study we show that these stalled spliceosomes are compromised for an essential conformational switch that is triggered by Prp16 helicase. These results suggest a plausible mechanistic basis for the second-step arrest in prp17Δ extracts and support a role for Prp17 in conjunction with Prp16. To understand the association of Prp17 with spliceosomes we used a functional epitope-tagged protein in co-immunoprecipitation experiments. Examination of co-precipitated snRNAs (small nuclear RNAs) show that Prp17 interacts with U2, U5 and U6 snRNPs (small nuclear ribonucleoproteins) but it is not a core component of any one snRNP. Prp17 association with in-vitro-assembled spliceosome complexes on actin pre-mRNAs was also investigated. Although the U5 snRNP proteins Prp8 and Snu114 are found in early pre-spliceosomes that contain all five snRNPs, Prp17 is not detectable at this step; however, Prp17 is present in the subsequent pre-catalytic A1 complex, containing unspliced pre-mRNA, formed after the dissociation of U4 snRNP. Thus Prp17 joins the spliceosome prior to both catalytic reactions. Our results indicate continued interactions in catalytic spliceosomes that contain reaction intermediates and in post-splicing complexes containing the lariat intron. These Prp17–spliceosome association analyses provide a biochemical basis for the delayed first step in prp17Δ and explain the previously known multiple genetic interactions between Prp17, factors of the Prp19-complex [NTC (nineteen complex)], functional elements in U2 and U5 snRNAs and other second-step splicing factors.

scholarly journals Pyrimidine tracts between the 5' splice site and branch point facilitate splicing and recognition of a small Drosophila intron.

1997 ◽  
Vol 17 (5) ◽  
pp. 2774-2780 ◽  
Author(s):  
C F Kennedy ◽  
S M Berget
Keyword(s):  
Drosophila Melanogaster ◽  
Branch Point ◽  
Splice Site ◽  
Minimum Size ◽  
Cross Linking ◽  
In Vitro Splicing ◽  
Precursor Rna ◽  
Minimal Region

The minimum size for splicing of a vertebrate intron is approximately 70 nucleotides. In Drosophila melanogaster, more than half of the introns are significantly below this minimum yet function well. Such short introns often lack the pyrimidine tract located between the branch point and 3' splice site common to metazoan introns. To investigate if small introns contain special sequences that facilitate their recognition, the sequences and factors required for the splicing of a 59-nucleotide intron from the D. melanogaster mle gene have been examined. This intron contains only a minimal region of interrupted pyrimidines downstream of the branch point. Instead, two longer, uninterrupted C-rich tracts are located between the 5' splice site and branch point. Both of these sequences are required for maximal in vivo and in vitro splicing. The upstream sequences are also required for maximal binding of factors to the 5' splice site, cross-linking of U2AF to precursor RNA, and assembly of the active spliceosome, suggesting that sequences upstream of the branch point influence events at both ends of the small mle intron. Thus, a very short intron lacking a classical pyrimidine tract between the branch point and 3' splice site requires accessory pyrimidine sequences in the short region between the 5' splice site and branch point.

Multiple interactions between the splicing substrate and small nuclear ribonucleoproteins in spliceosomes

1987 ◽  
Vol 7 (1) ◽  
pp. 281-293
Author(s):  
B Chabot ◽  
J A Steitz
Keyword(s):  
Splice Site ◽  
Beta Globin ◽  
Branch Site ◽  
U2 Snrnp ◽  
U1 Snrnp ◽  
Branch Formation ◽  
Splice Site Sequence ◽  
Multiple Interactions ◽  
Small Nuclear Ribonucleoproteins

Protection experiments with antibodies against small nuclear ribonucleoproteins (snRNPs) have elucidated the location of and requirements for interactions between snRNPs and human beta-globin transcripts during splicing in vitro. U2 snRNP association with the intron branch site continues after branch formation, requires intact U2 RNA, and is affected by some alterations of the 3' splice site sequence. U2 snRNP binding to the branched intermediate and U1 snRNP protection of an extended 5' splice region are detected exclusively in spliceosome fractions, indicating that both snRNPs are spliceosome components. While each snRNP associates specifically with the pre-mRNA, they also appear to interact with each other. The recovery of fragments mapping upstream of the 5' splice site suggests how the excised exon is held in the spliceosome.

Group II introns deleted for multiple substructures retain self-splicing activity

1992 ◽  
Vol 12 (5) ◽  
pp. 1950-1958
Author(s):  
J L Koch ◽  
S C Boulanger ◽  
S D Dib-Hajj ◽  
S K Hebbar ◽  
P S Perlman
Keyword(s):  
Binding Site ◽  
Splice Junction ◽  
Group Ii Introns ◽  
Splice Site Selection ◽  
Catalytic Core ◽  
Single Deletion ◽  
Group Ii ◽  
Precursor Rna ◽  
Self Splicing

Group II introns can be folded into highly conserved secondary structures with six major substructures or domains. Domains 1 and 5 are known to play key roles in self-splicing, while the roles of domains 2, 3, 4, and 6 are less clear. A trans assay for domain 5 function has been developed which indicates that domain 5 has a binding site on the precursor RNA that is not predicted from any secondary structure element. In this study, the self-splicing group II intron 5 gamma of the coxI gene of yeast mitochondrial DNA was deleted for various intron domains, singly and in combinations. Those mutant introns were characterized for self-splicing reactions in vitro as a means of locating the domain 5 binding site. A single deletion of domain 2, 3, 4, or 6 does not block in vitro reactions at either splice junction, though the deletion of domain 6 reduces the fidelity of 3' splice site selection somewhat. Even the triple deletion lacking domains 2, 4, and 6 retains some self-splicing activity. The deletion of domains 2, 3, 4, and 6 blocks the reaction at the 3' splice junction but not at the 5' junction. From these results, we conclude that the binding site for domain 5 is within domain 1 and that the complex of 5' exon, domain 1, and domain 5 (plus short connecting sequences) constitutes the essential catalytic core of this intron.

scholarly journals Multiple interactions between the splicing substrate and small nuclear ribonucleoproteins in spliceosomes.

1987 ◽  
Vol 7 (1) ◽  
pp. 281-293 ◽  
Author(s):  
B Chabot ◽  
J A Steitz
Keyword(s):  
Splice Site ◽  
Beta Globin ◽  
Branch Site ◽  
U2 Snrnp ◽  
U1 Snrnp ◽  
Branch Formation ◽  
Splice Site Sequence ◽  
Multiple Interactions ◽  
Small Nuclear Ribonucleoproteins

Protection experiments with antibodies against small nuclear ribonucleoproteins (snRNPs) have elucidated the location of and requirements for interactions between snRNPs and human beta-globin transcripts during splicing in vitro. U2 snRNP association with the intron branch site continues after branch formation, requires intact U2 RNA, and is affected by some alterations of the 3' splice site sequence. U2 snRNP binding to the branched intermediate and U1 snRNP protection of an extended 5' splice region are detected exclusively in spliceosome fractions, indicating that both snRNPs are spliceosome components. While each snRNP associates specifically with the pre-mRNA, they also appear to interact with each other. The recovery of fragments mapping upstream of the 5' splice site suggests how the excised exon is held in the spliceosome.

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