Thirteen Anti-Sm Monoclonal Antibodies Immunoprecipitate the Three Cytoplasmic snRNP Core Protein Precursors in Six Distinct Subsets

Fury, Matthew G.; Andersen, Jessica L.; Ponda, P.; Aimes, Ronald T.; Zieve, Gary W.

doi:10.1006/jaut.1998.0266

Cited by 12 publications

(10 citation statements)

References 32 publications

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“…Anti-Sm protein antibody immunoprecipitation experiments and Sm protein purification identified pre-snRNP Sm protein complexes of B/D3, D1/D2, and E/F/G (48,50). Our results show that in a 6S complex SmD3, but not SmB, is associated with pICln, and this is consistent with previous work showing that B and D3 are associated with each other in a 20S complex but not in a 6S complex (22,50,58). Our data show that SmD1 and SmD3 can interact with the 6S, JBP1-free pICln complex, and these associations do not require the carboxyl-terminal RG domains.…”

Section: Vol 21 2001supporting

confidence: 92%

“…The sizes of cytoplasmic intermediates in snRNP assembly containing Sm proteins have been studied by sucrose gradient centrifugation (22,23,50). To examine the fractionation of cytoplasmic pICln and JBP1 on sucrose gradients in FIG.…”

Section: Resultsmentioning

confidence: 99%

“…Based on pulse-chase experiments, it was proposed that the Sm proteins accumulate in 4S-6S complexes prior to assembly into snRNP core particles of approximately 11S (18). Subsequent work also identified SmB and SmD3 in an approximately 20S complex (1,22,50). Anti-Sm protein antibody immunoprecipitation experiments and Sm protein purification identified pre-snRNP Sm protein complexes of B/D3, D1/D2, and E/F/G (48,50).…”

Section: Vol 21 2001mentioning

confidence: 99%

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The Methylosome, a 20S Complex Containing JBP1 and pICln, Produces Dimethylarginine-Modified Sm Proteins

Friesen

Paushkin

Wyce

et al. 2001

Molecular and Cellular Biology

375

404

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snRNPs, integral components of the pre-mRNA splicing machinery, consist of seven Sm proteins which assemble in the cytoplasm as a ring structure on the snRNAs U1, U2, U4, and U5. The survival motor neuron (SMN) protein, the spinal muscular atrophy disease gene product, is crucial for snRNP core particle assembly in vivo. SMN binds preferentially and directly to the symmetrical dimethylarginine (sDMA)-modified arginineand glycine-rich (RG-rich) domains of SmD1 and SmD3. We found that the unmodified, but not the sDMAmodified, RG domains of SmD1 and SmD3 associate with a 20S methyltransferase complex, termed the methylosome, that contains the methyltransferase JBP1 and a JBP1-interacting protein, pICln. JBP1 binds SmD1 and SmD3 via their RG domains, while pICln binds the Sm domains. JBP1 produces sDMAs in the RG domain-containing Sm proteins. We further demonstrate the existence of a 6S complex that contains pICln, SmD1, and SmD3 but not JBP1. SmD3 from the methylosome, but not that from the 6S complex, can be transferred to the SMN complex in vitro. Together with previous results, these data indicate that methylation of Sm proteins by the methylosome directs Sm proteins to the SMN complex for assembly into snRNP core particles and suggest that the methylosome can regulate snRNP assembly.

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Section: Vol 21 2001supporting

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Section: Vol 21 2001mentioning

confidence: 99%

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The Methylosome, a 20S Complex Containing JBP1 and pICln, Produces Dimethylarginine-Modified Sm Proteins

Friesen

Paushkin

Wyce

et al. 2001

Molecular and Cellular Biology

375

404

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“…This implies that extensive protein rearrangements are required for stable core RNP formation and that these rearrangements are rate limiting during core assembly. The stepwise assembly of the Sm protein complexes onto U snRNA (8,36) is likely to be an important regulatory control for U snRNP core assembly and suggests two ways, which are not mutually exclusive, in which RNA-protein interactions may be necessary to trigger protein rearrangements prior to stable association with U snRNA. The first possibility is that the protein interaction surfaces of the EFG (and perhaps also of the D1D2 and B/BЈD3) complex are blocked for association with the other Sm complexes until an initial RNA-protein contact(s) exposes them.…”

Section: Discussionmentioning

confidence: 99%

“…Sm protein complexes assemble onto U snRNA in a stepwise and ordered manner. An initial and cooperative association of both the EFG and the D1D2 complexes with the U snRNA forms the U snRNP subcore particle (8,36). The U snRNP subcore is the only stable RNP intermediate formed during core RNP assembly and provides a unique binding site for the B/BЈD3 complex, whose association completes the core RNP particle (36,38).…”

mentioning

confidence: 99%

Spliceosomal U snRNP Core Assembly: Sm Proteins Assemble onto an Sm Site RNA Nonanucleotide in a Specific and Thermodynamically Stable Manner

Raker

Hartmuth

Kastner

et al. 1999

Molecular and Cellular Biology

135

164

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The association of Sm proteins with U small nuclear RNA (snRNA) requires the single-stranded Sm site (PuAU 4-6 GPu) but also is influenced by nonconserved flanking RNA structural elements. Here we demonstrate that a nonameric Sm site RNA oligonucleotide sufficed for sequence-specific assembly of a minimal core ribonucleoprotein (RNP), which contained all seven Sm proteins. The minimal core RNP displayed several conserved biochemical features of native U snRNP core particles, including a similar morphology in electron micrographs. This minimal system allowed us to study in detail the RNA requirements for Sm protein-Sm site interactions as well as the kinetics of core RNP assembly. In addition to the uridine bases, the 2 hydroxyl moieties were important for stable RNP formation, indicating that both the sugar backbone and the bases are intimately involved in RNA-protein interactions. Moreover, our data imply that an initial phase of core RNP assembly is mediated by a high affinity of the Sm proteins for the single-stranded uridine tract but that the presence of the conserved adenosine (PuAU. . .) is essential to commit the RNP particle to thermodynamic stability. Comparison of intact U4 and U5 snRNAs with the Sm site oligonucleotide in core RNP assembly revealed that the regions flanking the Sm site within the U snRNAs facilitate the kinetics of core RNP assembly by increasing the rate of Sm protein association and by decreasing the activation energy.Small nuclear ribonucleoproteins (snRNPs) mediate essential RNA processing events, including pre-mRNA splicing (reviewed in references 43 and 45). The major spliceosomal snRNP particles consist of snRNA (U1, U2, U4/U6, or U5) and numerous proteins, which can be classified as either snRNP specific or common to each snRNP particle. The common proteins are collectively referred to as Sm proteins and were originally identified due to their antigenicity in the autoimmune disease systemic lupus erythematosus (26). The best characterized of these are the seven HeLa Sm proteins, which are named B/BЈ, D1, D2, D3, E, F, and G and range in size from 241 (for BЈ) to 76 (for G) amino acids (reference 16 and references therein). B and BЈ are alternatively spliced products of the same gene, differing only in 11 amino acids at their C termini (42), and are referred to here as B/BЈ.Association of the Sm proteins with U snRNA plays a pivotal role in the further biogenesis of U snRNP particles. The metabolic stability of the U snRNP particles is dependent on the Sm protein association (10,20,37). Following export from the nucleus, each U snRNA (with the exception of U6) assembles cytoplasmically with a set of Sm proteins, resulting in its core RNP particle. Hypermethylation of the U snRNA 5Ј cap structure from monomethyl guanosine (m 7 G) to trimethylguanosine (m 3 G) is dependent upon formation of the core RNP domain, and in particular requires the presence of the B/BЈ and D3 Sm proteins (30,34,36). These Sm proteins are the last to assemble (36, 38), linking cap hypermethylation to th...

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The Cytoplasmic Sites of the snRNP Protein Complexes Are Punctate Structures That Are Responsive to Changes in Metabolism and Intracellular Architecture

Zieve

1999

Experimental Cell Research

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Thirteen Anti-Sm Monoclonal Antibodies Immunoprecipitate the Three Cytoplasmic snRNP Core Protein Precursors in Six Distinct Subsets

Cited by 12 publications

References 32 publications

The Methylosome, a 20S Complex Containing JBP1 and pICln, Produces Dimethylarginine-Modified Sm Proteins

The Methylosome, a 20S Complex Containing JBP1 and pICln, Produces Dimethylarginine-Modified Sm Proteins

Spliceosomal U snRNP Core Assembly: Sm Proteins Assemble onto an Sm Site RNA Nonanucleotide in a Specific and Thermodynamically Stable Manner

The Cytoplasmic Sites of the snRNP Protein Complexes Are Punctate Structures That Are Responsive to Changes in Metabolism and Intracellular Architecture

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