A Novel Function for SMN, the Spinal Muscular Atrophy Disease Gene Product, in Pre-mRNA Splicing

Pellizzoni, Livio; Kataoka, Naoyuki; Charroux, Bernard; Dreyfuss, Gideon

doi:10.1016/s0092-8674(00)81632-3

Cited by 502 publications

(485 citation statements)

References 54 publications

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“…In this context, it is noteworthy that one Cajal body protein, hPrp24/SART3/p110, has been implicated in U4/ U6 recycling (Bell et al 2002;Stanek et al 2003). Similarly, SMN and its associated proteins may also help to ensure that the Sm core is properly reformed onto the snRNA following splicing (Matera 1999;Pellizzoni et al 1998).…”

Section: Discussionmentioning

confidence: 99%

The C-terminal domain of coilin interacts with Sm proteins and U snRNPs

Pillai

Azzouz

et al. 2005

Chromosoma

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Coilin is the signature protein of the Cajal body (CB), a nuclear suborganelle involved in the biogenesis of small nuclear ribonucleoproteins (snRNPs). Newly imported Sm-class snRNPs are thought to traffic through CBs before proceeding to their final nuclear destinations. Loss of coilin function in mice leads to significant viability and fertility problems. Coilin interacts directly with the spinal muscular atrophy (SMA) protein via dimethylarginine residues in its C-terminal domain. Although coilin hypomethylation results in delocalization of survival of motor neurons (SMN) from CBs, high concentrations of snRNPs remain within these structures. Thus, CBs appear to be involved in snRNP maturation, but factors that tether snRNPs to CBs have not been described. In this report, we demonstrate that the coilin C-terminal domain binds directly to various Sm and Lsm proteins via their Sm motifs. We show that the region of coilin responsible for this binding activity is separable from that which binds to SMN. Interestingly, U2, U4, U5, and U6 snRNPs interact with the coilin C-terminal domain in a glutathione S-transferase (GST)-pulldown assay, whereas U1 and U7 snRNPs do not. Thus, the ability to interact with free Sm (and Lsm) proteins as well as with intact snRNPs, indicates that coilin and CBs may facilitate the modification of newly formed snRNPs, the regeneration of 'mature' snRNPs, or the reclamation of unassembled snRNP components.

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Section: Discussionmentioning

confidence: 99%

The C-terminal domain of coilin interacts with Sm proteins and U snRNPs

Pillai

Azzouz

et al. 2005

Chromosoma

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“…Injection of Gemin2-specific monoclonal antibodies inhibited, whereas injection of SMN-specific monoclonal antibodies stimulated, snRNP biogenesis (31). In HeLa cells SMN deleted of the amino-terminal 27 amino acids (SMN⌬N27) functions as a dominant negative mutant sequestering the SMN complex in large cytoplasmic and nuclear bodies (32). SMN⌬N27 causes accumulation of Sm proteins and U snRNA in the cytoplasm, suggesting that this mutant blocks snRNP assembly prior to cap hypermethylation and nuclear import.…”

mentioning

confidence: 99%

“…SMN⌬N27 causes accumulation of Sm proteins and U snRNA in the cytoplasm, suggesting that this mutant blocks snRNP assembly prior to cap hypermethylation and nuclear import. In vitro SMN stimulates, whereas SMN⌬N27 and anti-SMN antibodies inhibit, splicing following preincubation in nuclear extracts, demonstrating that SMN may have a role in nuclear regeneration of snRNPs (32). SnRNP assembly and nuclear splicing are basic cellular functions required for cellular viability.…”

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confidence: 99%

Specific Sequences of the Sm and Sm-like (Lsm) Proteins Mediate Their Interaction with the Spinal Muscular Atrophy Disease Gene Product (SMN)

Friesen

Dreyfuss

2000

Journal of Biological Chemistry

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112

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The spinal muscular atrophy disease gene product (SMN) is crucial for small nuclear ribonuclear protein (snRNP) biogenesis in the cytoplasm and plays a role in pre-mRNA splicing in the nucleus. SMN oligomers interact avidly with the snRNP core proteins SmB, -D1, and -D3. We have delineated the specific sequences in the Sm proteins that mediate their interaction with SMN. We show that unique carboxyl-terminal arginine-and glycine-rich domains comprising the last 29 amino acids of SmD1 and the last 32 amino acids of SmD3 are necessary and sufficient for SMN binding. Interestingly, SMN also interacts with at least two of the U6-associated Sm-like (Lsm) proteins, Lsm4 and Lsm6. Furthermore, the carboxyl-terminal arginine-and glycine-rich domain of Lsm4 directly interacts with SMN. This suggests that SMN also functions in the assembly of the U6 snRNP in the nucleus and in the assembly of other Lsm-containing complexes. These findings demonstrate that arginineand glycine-rich domains are necessary and sufficient for SMN interaction, and they expand further the range of targets of the SMN protein.Spinal muscular atrophy (SMA) 1 is a neuromuscular disease that results in muscular weakness and atrophy due to degeneration of motor neurons of the spinal cord (1-4). Over 98% of SMA patients have mutations or deletions of the Survival Motor Neuron (SMN1) gene, which is present as an inverted repeat on chromosome 5 at 5q13 (5-7). Only deletions or mutations in the telomeric copy of SMN (SMN1) lead to SMA (7)(8)(9)(10)(11)(12)(13)(14). The centromeric copy of the gene (SMN2) produces mostly an alternatively spliced form of SMN deleted of amino acids encoded by exon 7 (SMN⌬Ex7), and SMN2 can only partially compensate for mutations or deletions in SMN1 (7,15,16). Indeed, some patients, instead of complete deletion of SMN1, have shorter deletions of at least exon 7 or single point mutations within the conserved YG domain (17,18).As measured by coimmunoprecipitation from cytoplasmic extracts, SMN exists in a complex with Sm proteins (19), Gemin2 (formerly SIP1) (19), Gemin4 (20), and the DEAD box RNA helicase Gemin3 (21). The amino terminus of SMN tightly associates with Gemin2, whereas the carboxyl-terminal conserved YG domain is necessary for self-association and interaction with the core snRNP Sm proteins (19,22). We have recently demonstrated that oligomerization of SMN through the conserved YG domain is required for efficient interaction with SmB, -D1, and -D3 and suggested that upon oligomerization a high affinity Sm protein binding site is formed (23).SnRNPs are formed in the cytoplasm where the core Sm proteins bind to the Sm site on U snRNA, and following hypermethylation of the m 7 G cap to a 2,2,7-trimethyl-gaunosine (m 3 G) cap the snRNP is transported to the nucleus (24 -30). Using oocyte injections, it was demonstrated that the SMN⅐Gemin2 complex plays a role in spliceosomal snRNP assembly that takes place in the cytoplasm. Injection of Gemin2-specific monoclonal antibodies inhibited, whereas injection of SMN-specifi...

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“…601627), differ in only one base. 2 This C-to-T substitution in SMN2 exon 7 affects the activity of an exonic splice enhancer and alters the splicing pattern of SMN2 mRNA, 3 resulting in a lower level of full-length SMN transcript from SMN2 than from SMN1. 4 -6 SMN2 was shown to be unique to Homo sapiens.…”

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confidence: 99%

Quantification of PCR Bias Caused by a Single Nucleotide Polymorphism in SMN Gene Dosage Analysis

Ogino

Wilson

2002

The Journal of Molecular Diagnostics

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Approximately 94% of patients with spinal muscular atrophy lack both copies of SMN1 exon 7, and most carriers have only one copy of SMN1 exon 7. We described previously the effect of SMN1/SMN2 heteroduplex formation on SMN gene dosage analysis, which is a multiplex quantitative PCR assay to determine the copy numbers of SMN1 and SMN2 using DraI digestion to differentiate SMN2 from SMN1. We describe herein the quantification of PCR bias between SMN1 exon 7 and SMN2 exon 7, which differ by only one nucleotide that is not present in either primer binding site. Using samples from 272 individuals with various SMN genotypes, we found that the amplification efficiency of SMN2 was consistent only approximately 80% that of SMN1. Thus, even a single nucleotide polymorphism, not in primer binding sites, can cause reproducible PCR bias. The precision and accuracy of our SMN gene dosage analysis are high because our assay design and controls take advantage of the consistency of the PCR bias. As additional clinically significant single nucleotide polymorphisms (SNPs) are discovered, assessment of PCR bias, and judicious selection of standards and controls, will be increasingly important for quantitative PCR assays. Spinal muscular atrophy (SMA: type I, MIM no. 253300; type II, MIM no. 253550; type III, MIM no. 253400) is an autosomal recessive disorder associated with loss of motor neurons in the anterior horn of the spinal cord and caused by mutations in the Survival Motor Neuron 1 gene (SMN1; MIM no. 600354) on 5q13. 1 Coding regions of SMN1 and its centromeric homologue, SMN2 (MIM no. 601627), differ in only one base. 2 This C-to-T substitution in SMN2 exon 7 affects the activity of an exonic splice enhancer and alters the splicing pattern of SMN2 mRNA, 3 resulting in a lower level of full-length SMN transcript from SMN2 than from SMN1. 4 -6 SMN2 was shown to be unique to Homo sapiens. 7 Approximately 94% of clinically typical SMA patients lack both copies of SMN1 exon 7. 8 SMN gene dosage analysis, a method to determine the copy number of SMN1, can be used to identify SMA carriers. Exon 7 of SMN1 and SMN2 are co-amplified with genomic and internal standards. The PCR products are then digested with DraI, which cuts only SMN2 exon 7 PCR products, followed by quantification of the PCR products. 9 -11 Other methods for SMN gene dosage analysis have been described. 12-14 A single copy of SMN1 by gene dosage analysis confirms carrier status; this analysis is therefore of clinical importance. A single-copy result also supports the diagnosis of SMN1-related SMA in an affected individual, who may have one deleted allele and one allele with a small intragenic mutation. However, the final diagnosis depends largely on the index of clinical suspicion. 15 This is because the frequency of single-copy carriers in the general population (ϳ2%) approaches the frequency of individuals affected with SMN1-related SMA who have a single-copy test result (ϳ3.6% 12 ). 16 The copy number of SMN2 correlates inversely with disease severity. 9,10,[12]...

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A Novel Function for SMN, the Spinal Muscular Atrophy Disease Gene Product, in Pre-mRNA Splicing

Cited by 502 publications

References 54 publications

The C-terminal domain of coilin interacts with Sm proteins and U snRNPs

The C-terminal domain of coilin interacts with Sm proteins and U snRNPs

Specific Sequences of the Sm and Sm-like (Lsm) Proteins Mediate Their Interaction with the Spinal Muscular Atrophy Disease Gene Product (SMN)

Quantification of PCR Bias Caused by a Single Nucleotide Polymorphism in SMN Gene Dosage Analysis

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