Structural basis of branch site recognition by the human spliceosome

Science ◽  
2022 ◽  
Vol 375 (6576) ◽  
pp. 50-57
Author(s):  
Jonas Tholen ◽  
Michal Razew ◽  
Felix Weis ◽  
Wojciech P. Galej
Keyword(s):  
Structural Basis ◽  
Branch Site ◽  
Site Recognition

An mRNA-type intron is present in the Rhodotorula hasegawae U2 small nuclear RNA gene

1993 ◽  
Vol 13 (9) ◽  
pp. 5613-5619
Author(s):  
Y Takahashi ◽  
S Urushiyama ◽  
T Tani ◽  
Y Ohshima
Keyword(s):  
Mrna Splicing ◽  
Small Nuclear Rna ◽  
U2 Snrna ◽  
U6 Snrna ◽  
Branch Site ◽  
Snrna Gene ◽  
Nuclear Rna ◽  
Catalytic Role ◽  
Mrna Precursor ◽  
Site Recognition

Splicing an mRNA precursor requires multiple factors involving five small nuclear RNA (snRNA) species called U1, U2, U4, U5, and U6. The presence of mRNA-type introns in the U6 snRNA genes of some yeasts led to the hypothesis that U6 snRNA may play a catalytic role in pre-mRNA splicing and that the U6 introns occurred through reverse splicing of an intron from an mRNA precursor into a catalytic site of U6 snRNA. We characterized the U2 snRNA gene of the yeast Rhodotorula hasegawae, which has four mRNA-type introns in the U6 snRNA gene, and found an mRNA-type intron of 60 bp. The intron of the U2 snRNA gene is present in the highly conserved region immediately downstream of the branch site recognition domain. Interestingly, we found that this region can form a novel base pairing with U6 snRNA. We discuss the possible implications of these findings for the mechanisms of intron acquisition and for the role of U2 snRNA in pre-mRNA splicing.

scholarly journals U2 small nuclear RNA 3' end formation is directed by a critical internal structure distinct from the processing site.

1993 ◽  
Vol 13 (2) ◽  
pp. 1119-1129 ◽  
Author(s):  
M R Jacobson ◽  
M Rhoadhouse ◽  
T Pederson
Keyword(s):  
Rna Processing ◽  
Minor Effect ◽  
Small Nuclear Rna ◽  
Recognition Sequence ◽  
Stem Loop ◽  
Branch Site ◽  
Nuclear Rna ◽  
A Minor ◽  
Site Recognition

Mature U2 small nuclear RNA is generated by the removal of 11 to 12 nucleotides from the 3' end of the primary transcript. This pre-U2 RNA processing reaction takes place in the cytoplasm. In this study, the sequences and/or structures of pre-U2 RNA that are important for 3' processing have been examined in an in vitro system. The 7-methylguanosine cap, stem-loops I and II, the lariat branch site recognition sequence, the conserved Sm domain, and several other regions throughout the 5' end of U2 RNA have no apparent role in the 3' processing reaction. In fact, deletion of the entire first 104 nucleotides resulted in mini-pre-U2 RNAs which were efficiently processed. Similarly, deletion of the top two-thirds of stem-loop III or mutation of nucleotides in the loop of stem-loop IV had little effect on 3' processing. Most surprisingly, the precursor's 11- to 12-nucleotide 3' extension itself was of relatively little importance, since this sequence could be replaced with completely different sequences with only a minor effect on the 3' processing reaction. In contrast, we have defined a critical structure consisting of the bottom of stem III and the stem of stem-loop IV that is essential for 3' processing of pre-U2 RNA. Compensatory mutations which restore base pairing in this region resulted in normal 3' processing. Thus, although the U2 RNA processing activity recognizes the bottom of stem III and stem IV, the sequence of this critical region is much less important than its structure. These results, together with the surprising observation that the reaction is relatively indifferent to the sequence of the 11- to 12-nucleotide 3' extension itself, point to a 3' processing reaction of pre-U2 RNA that has sequence and structure requirements significantly different from those previously identified for pre-mRNA 3' processing.

scholarly journals An mRNA-type intron is present in the Rhodotorula hasegawae U2 small nuclear RNA gene.

1993 ◽  
Vol 13 (9) ◽  
pp. 5613-5619 ◽  
Author(s):  
Y Takahashi ◽  
S Urushiyama ◽  
T Tani ◽  
Y Ohshima
Keyword(s):  
Mrna Splicing ◽  
Small Nuclear Rna ◽  
U2 Snrna ◽  
U6 Snrna ◽  
Branch Site ◽  
Snrna Gene ◽  
Nuclear Rna ◽  
Catalytic Role ◽  
Mrna Precursor ◽  
Site Recognition

Splicing an mRNA precursor requires multiple factors involving five small nuclear RNA (snRNA) species called U1, U2, U4, U5, and U6. The presence of mRNA-type introns in the U6 snRNA genes of some yeasts led to the hypothesis that U6 snRNA may play a catalytic role in pre-mRNA splicing and that the U6 introns occurred through reverse splicing of an intron from an mRNA precursor into a catalytic site of U6 snRNA. We characterized the U2 snRNA gene of the yeast Rhodotorula hasegawae, which has four mRNA-type introns in the U6 snRNA gene, and found an mRNA-type intron of 60 bp. The intron of the U2 snRNA gene is present in the highly conserved region immediately downstream of the branch site recognition domain. Interestingly, we found that this region can form a novel base pairing with U6 snRNA. We discuss the possible implications of these findings for the mechanisms of intron acquisition and for the role of U2 snRNA in pre-mRNA splicing.

U2 small nuclear RNA 3' end formation is directed by a critical internal structure distinct from the processing site

1993 ◽  
Vol 13 (2) ◽  
pp. 1119-1129
Author(s):  
M R Jacobson ◽  
M Rhoadhouse ◽  
T Pederson
Keyword(s):  
Rna Processing ◽  
Minor Effect ◽  
Small Nuclear Rna ◽  
Recognition Sequence ◽  
Stem Loop ◽  
Branch Site ◽  
Nuclear Rna ◽  
A Minor ◽  
Site Recognition

Mature U2 small nuclear RNA is generated by the removal of 11 to 12 nucleotides from the 3' end of the primary transcript. This pre-U2 RNA processing reaction takes place in the cytoplasm. In this study, the sequences and/or structures of pre-U2 RNA that are important for 3' processing have been examined in an in vitro system. The 7-methylguanosine cap, stem-loops I and II, the lariat branch site recognition sequence, the conserved Sm domain, and several other regions throughout the 5' end of U2 RNA have no apparent role in the 3' processing reaction. In fact, deletion of the entire first 104 nucleotides resulted in mini-pre-U2 RNAs which were efficiently processed. Similarly, deletion of the top two-thirds of stem-loop III or mutation of nucleotides in the loop of stem-loop IV had little effect on 3' processing. Most surprisingly, the precursor's 11- to 12-nucleotide 3' extension itself was of relatively little importance, since this sequence could be replaced with completely different sequences with only a minor effect on the 3' processing reaction. In contrast, we have defined a critical structure consisting of the bottom of stem III and the stem of stem-loop IV that is essential for 3' processing of pre-U2 RNA. Compensatory mutations which restore base pairing in this region resulted in normal 3' processing. Thus, although the U2 RNA processing activity recognizes the bottom of stem III and stem IV, the sequence of this critical region is much less important than its structure. These results, together with the surprising observation that the reaction is relatively indifferent to the sequence of the 11- to 12-nucleotide 3' extension itself, point to a 3' processing reaction of pre-U2 RNA that has sequence and structure requirements significantly different from those previously identified for pre-mRNA 3' processing.

scholarly journals Alternative splicing of a human alpha-tropomyosin muscle-specific exon: identification of determining sequences.

1992 ◽  
Vol 12 (9) ◽  
pp. 3872-3882 ◽  
Author(s):  
I R Graham ◽  
M Hamshere ◽  
I C Eperon
Keyword(s):  
Skeletal Muscle ◽  
Alternative Splicing ◽  
Splice Site ◽  
Sequence Effect ◽  
Cos Cells ◽  
Branch Site ◽  
Exon Sequence ◽  
Site Recognition

The human alpha-tropomyosin gene hTMnm has two mutually exclusive versions of exon 5 (NM and SK), one of which is expressed specifically in skeletal muscle (exon SK). A minigene construct expresses only the nonmuscle (NM) isoform when transfected into COS-1 cells and both forms when transfected into myoblasts. Twenty-four mutants were produced to determine why the SK exon is not expressed in COS cells. The results showed that exons NM and SK are not in competition for splicing to the flanking exons and that there is no intrinsic barrier to splicing between the exons. Instead, exon SK is skipped whenever there are flanking introns. Splicing of exon SK was induced when the branch site sequence 70 nucleotides upstream of the exon was mutated to resemble the consensus and when the extremities of the exon itself were changed to the corresponding NM sequence. Precise swaps of the NM and SK exon sequences showed that the exon sequence effect was dominant to that of intron sequences. The mechanism of regulation appears to be unlike that of other tropomyosin genes. We propose that exclusion of exon SK arises because its 3' splicing signals are weak and are prevented by an exon-specific repressor from competing for splice site recognition.

scholarly journals Structural basis of intron selection by U2 snRNP in the presence of covalent inhibitors

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Constantin Cretu ◽  
Patricia Gee ◽  
Xiang Liu ◽  
Anant Agrawal ◽  
Tuong-Vi Nguyen ◽  
...  
Keyword(s):  
Structural Basis ◽  
Critical Event ◽  
Dependent Manner ◽  
Branch Site ◽  
Small Nuclear Ribonucleoprotein ◽  
U2 Snrnp ◽  
Covalent Inhibitors ◽  
Intron Recognition ◽  
Chemical Modulation ◽  
Nuclear Ribonucleoprotein

AbstractIntron selection during the formation of prespliceosomes is a critical event in pre-mRNA splicing. Chemical modulation of intron selection has emerged as a route for cancer therapy. Splicing modulators alter the splicing patterns in cells by binding to the U2 snRNP (small nuclear ribonucleoprotein)—a complex chaperoning the selection of branch and 3′ splice sites. Here we report crystal structures of the SF3B module of the U2 snRNP in complex with spliceostatin and sudemycin FR901464 analogs, and the cryo-electron microscopy structure of a cross-exon prespliceosome-like complex arrested with spliceostatin A. The structures reveal how modulators inactivate the branch site in a sequence-dependent manner and stall an E-to-A prespliceosome intermediate by covalent coupling to a nucleophilic zinc finger belonging to the SF3B subunit PHF5A. These findings support a mechanism of intron recognition by the U2 snRNP as a toehold-mediated strand invasion and advance an unanticipated drug targeting concept.

Alternative splicing of a human alpha-tropomyosin muscle-specific exon: identification of determining sequences

1992 ◽  
Vol 12 (9) ◽  
pp. 3872-3882
Author(s):  
I R Graham ◽  
M Hamshere ◽  
I C Eperon
Keyword(s):  
Skeletal Muscle ◽  
Alternative Splicing ◽  
Splice Site ◽  
Sequence Effect ◽  
Cos Cells ◽  
Branch Site ◽  
Exon Sequence ◽  
Site Recognition

The human alpha-tropomyosin gene hTMnm has two mutually exclusive versions of exon 5 (NM and SK), one of which is expressed specifically in skeletal muscle (exon SK). A minigene construct expresses only the nonmuscle (NM) isoform when transfected into COS-1 cells and both forms when transfected into myoblasts. Twenty-four mutants were produced to determine why the SK exon is not expressed in COS cells. The results showed that exons NM and SK are not in competition for splicing to the flanking exons and that there is no intrinsic barrier to splicing between the exons. Instead, exon SK is skipped whenever there are flanking introns. Splicing of exon SK was induced when the branch site sequence 70 nucleotides upstream of the exon was mutated to resemble the consensus and when the extremities of the exon itself were changed to the corresponding NM sequence. Precise swaps of the NM and SK exon sequences showed that the exon sequence effect was dominant to that of intron sequences. The mechanism of regulation appears to be unlike that of other tropomyosin genes. We propose that exclusion of exon SK arises because its 3' splicing signals are weak and are prevented by an exon-specific repressor from competing for splice site recognition.

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