GO:0120114 Sm-like protein family complex: Components, Assembly and Research Methods, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0120114 defines the Sm-like protein family complex, a cellular component comprising Sm and Lsm proteins that form hexameric or heptameric rings binding RNA [1, 2, 3].
• These complexes are ancient, with homologs in bacteria (Hfq) and archaea, and are essential for RNA processing and degradation [1, 4, 5].
• The Sm ring is a core component of spliceosomal snRNPs (U1, U2, U4, U5, U6), while Lsm rings function in mRNA decapping and 3' end processing [2, 6, 7].
• Sm and Lsm proteins share an Sm domain that binds oligo(U) RNA with high specificity.
• Dysregulation of Sm-like complexes is linked to diseases including cancer, neurodegeneration, and splicing-related disorders.
• CRISPR-based knockout, knock-in, and overexpression models are powerful tools to study the function of Sm-like complex components [6, 7].
Description
The Sm-like protein family complex (GO:0120114) is a cellular component defined by the presence of Sm and Lsm proteins, which assemble into hexameric or heptameric rings that bind RNA [1, 2, 3]. These complexes are evolutionarily ancient, with bacterial Hfq and archaeal Sm proteins serving as structural and functional homologs [1, 4]. The Sm ring is a hallmark of spliceosomal small nuclear ribonucleoproteins (snRNPs), which are essential for pre-mRNA splicing, while Lsm rings participate in mRNA decapping, 3' end processing, and degradation [2, 5, 6]. Researchers study these complexes to understand fundamental RNA metabolism and their roles in human disease, including cancer and neurodegeneration [6, 7].
Sm-like protein family complex At A Glance
| GO ID | GO:0120114 |
|---|---|
| GO term | Sm-like protein family complex |
| Ontology | cellular_component |
| Synonym | None |
| Major function | RNA binding, pre-mRNA splicing, mRNA decapping and degradation |
| Evolutionary conservation | Present in bacteria (Hfq), archaea, and eukaryotes [1, 4] |
| Structural feature | Hexameric or heptameric ring [2, 3] |
| Key components | Sm proteins (B/B', D1, D2, D3, E, F, G) and Lsm proteins (Lsm1-8) [2, 6] |
| Associated diseases | Cancer, neurodegeneration, splicing disorders |
What Is GO:0120114?
The Sm-like protein family complex is a protein complex that contains members of the Like-Sm (Lsm) family, including both Sm and Lsm proteins. These proteins typically form hexameric or heptameric ring structures that bind RNA. Some rings can form independently of RNA, but many require RNA for assembly. In addition to Lsm-family proteins, these complexes often include other protein components. Examples include the snRNPs of the spliceosome and complexes involved in 5' to 3' mRNA degradation in the cytoplasm and nucleus [1, 2, 3].
Why Is Sm-like protein family complex Important in Cell Biology?
The Sm-like protein family complex is central to RNA metabolism, influencing nearly every aspect of gene expression from splicing to decay [2, 5, 6]. Its dysfunction is linked to a growing list of human diseases, making it a critical area of research for understanding disease mechanisms and developing therapeutic interventions [6, 7].
• Essential for pre-mRNA splicing as core components of snRNPs.
• Critical for mRNA decapping and 5' to 3' degradation in the cytoplasm.
• Involved in nuclear degradation of unspliced transcripts.
• Mutations in Sm-like complex genes are associated with cancers and neurodegenerative diseases.
• Serves as a model for studying RNA-protein interactions and ring assembly [3, 8].
• Target for CRISPR-based functional genomics to dissect RNA processing pathways [6, 7].
• Evolutionarily conserved from bacteria to humans, enabling cross-species studies [1, 4].
• Plays a role in small RNA pathways and RNA quality control.
What Happens During Sm-like protein family complex?
Assembly of Sm and Lsm Rings
In simple terms: Sm and Lsm proteins come together to form ring-shaped structures that can grab onto RNA.
Sm and Lsm proteins assemble into hexameric or heptameric rings. In eukaryotes, the Sm ring consists of seven Sm proteins (B/B', D1, D2, D3, E, F, G) that form a toroidal structure. Lsm rings are composed of Lsm1-7 or Lsm2-8 proteins. Assembly often requires RNA, particularly for Lsm complexes, and is facilitated by chaperones [3, 5].
RNA Binding and Target Recognition
In simple terms: The ring binds to specific sequences on RNA, often rich in uridine, to identify targets.
The Sm domain binds oligo(U) sequences with high specificity. This binding is essential for snRNP function in splicing and for Lsm-mediated mRNA decay [2, 7]. The ring structure provides a platform for additional proteins to bind and execute downstream functions.
Spliceosomal snRNP Function
In simple terms: Sm rings are part of the splicing machinery that removes introns from pre-mRNA.
Sm proteins are core components of U1, U2, U4, U5, and U6 snRNPs. These snRNPs assemble into the spliceosome, which catalyzes intron removal. The Sm ring binds to the snRNA and is required for snRNP stability and function [2, 3].
mRNA Decapping and Degradation
In simple terms: Lsm rings help degrade mRNA by removing the protective cap and chewing it up.
The Lsm1-7 complex promotes decapping of mRNAs in the cytoplasm, leading to 5' to 3' degradation. In the nucleus, the Lsm2-8 complex associates with U6 snRNA and functions in pre-mRNA splicing and degradation of unspliced transcripts [5, 6].
Key Genes Involved in GO:0120114 Sm-like protein family complex
The following genes encode core components of the Sm-like protein family complex, including Sm and Lsm proteins, as well as associated factors.
| Gene | Major Role | Research Relevance |
|---|---|---|
| SNRPB | Sm protein B/B' | Core component of snRNPs; mutations linked to splicing disorders |
| SNRPD1 | Sm protein D1 | Essential for snRNP assembly; knockout causes splicing defects |
| SNRPD2 | Sm protein D2 | Part of Sm ring; required for pre-mRNA splicing |
| SNRPD3 | Sm protein D3 | Sm core component; involved in snRNP biogenesis |
| SNRPE | Sm protein E | Sm ring subunit; mutations associated with diseases |
| SNRPF | Sm protein F | Sm ring subunit; required for snRNP function |
| SNRPG | Sm protein G | Sm ring subunit; essential for splicing |
| LSM1 | Lsm protein 1 | Part of Lsm1-7 complex; functions in mRNA decapping |
| LSM2 | Lsm protein 2 | Part of Lsm2-8 complex; binds U6 snRNA |
| LSM3 | Lsm protein 3 | Lsm complex component; involved in RNA processing |
| LSM4 | Lsm protein 4 | Lsm complex component; role in splicing and decay |
| LSM5 | Lsm protein 5 | Lsm complex component; interacts with U6 snRNA |
| LSM6 | Lsm protein 6 | Lsm complex component; involved in mRNA decay |
| LSM7 | Lsm protein 7 | Lsm complex component; part of decapping machinery |
| LSM8 | Lsm protein 8 | Lsm complex component; nuclear function in splicing |
| HFQ | Bacterial Sm-like protein | RNA chaperone; mediates RNA-RNA interactions |
| SMAP | Archaeal Sm protein | Structural homolog; provides evolutionary insights |
How Is Sm-like protein family complex Regulated?
The assembly and function of Sm-like protein family complexes are regulated at multiple levels. Sm protein assembly is facilitated by the survival of motor neuron (SMN) complex, which is essential for snRNP biogenesis. Lsm complex formation can be regulated by RNA availability and post-translational modifications. Additionally, the activity of these complexes in mRNA decay is influenced by signaling pathways that control decapping enzyme activity.
Sm-like protein family complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| SNRPB | Cerebrocostomandibular syndrome | Knockout mouse, patient-derived iPSCs |
| LSM1 | Cancer progression | Overexpression in cancer cell lines, xenografts |
| LSM2 | Splicing defects in neurodegeneration | CRISPR knockout in neuronal cells |
| SMN1 | Spinal muscular atrophy | Knockout mouse, iPSC-derived motor neurons |
| HFQ | Bacterial virulence | Bacterial knockout models |
Sm-like Complexes in Cancer
Dysregulation of Sm and Lsm proteins has been observed in various cancers. For example, overexpression of Lsm proteins is associated with poor prognosis in some tumors, and splicing factor mutations are common in myeloid malignancies. Targeting these complexes may offer therapeutic opportunities.
Neurodegenerative Diseases
Mutations in Sm proteins can cause spinal muscular atrophy (SMA) due to defective snRNP assembly, and Lsm proteins are implicated in RNA metabolism defects linked to amyotrophic lateral sclerosis (ALS). The Sm-like complex is thus critical for neuronal survival.
Splicing Disorders
Mutations in genes encoding Sm proteins, such as SNRPB, have been linked to cerebrocostomandibular syndrome, a rare developmental disorder characterized by craniofacial and skeletal abnormalities. This highlights the importance of Sm ring integrity in human development.
From Sm-like protein family complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the role of Sm ring in splicing? | Knockout of SNRPB in HeLa cells followed by RNA-seq |
| How does Lsm1-7 affect mRNA stability? | Point mutation in LSM1 decapping motif, half-life assays |
| Does a disease-associated mutation affect snRNP assembly? | Knock-in of patient mutation in iPSCs |
| Where is Lsm complex localized? | Tagged knock-in of LSM2 with GFP for imaging |
| Can overexpression of Lsm proteins drive cancer? | Overexpression of LSM1 in mouse models |
| What are the interaction partners of Sm proteins? | Knockout followed by proteomics |
How to Study the Sm-like protein family complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| RNA-seq | Gene expression changes | Assess splicing defects upon Sm knockout |
| RIP-seq | RNA targets of Sm/Lsm proteins | Identify binding sites in mRNAs |
| Mass spectrometry | Protein interactions | Determine complex composition |
| CRISPR knockout | Gene function | Study essentiality of Sm genes |
| CRISPR knock-in | Mutant protein expression | Model disease mutations |
| Overexpression | Gain-of-function effects | Test oncogenic potential |
| Cryo-EM | 3D structure | Visualize ring assembly |
RNA Immunoprecipitation (RIP)
RIP using antibodies against Sm or Lsm proteins can identify bound RNAs. This method reveals the RNA targets of these complexes and their role in splicing and decay [2, 7].
Proteomics and Mass Spectrometry
Affinity purification of Sm-like complexes followed by mass spectrometry identifies associated proteins and post-translational modifications, providing insights into complex composition and regulation [3, 5].
CRISPR Screening
Genome-wide CRISPR knockout screens can identify genes that are essential for Sm-like complex function or that synthetically interact with complex components, uncovering new regulatory pathways.
Structural Biology
X-ray crystallography and cryo-EM have elucidated the ring structures of Sm and Lsm complexes, revealing how they bind RNA and assemble [4, 8].
How CRISPR Can Be Used to Study GO:0120114 Sm-like protein family complex
Knockout
CRISPR knockout of Sm or Lsm genes can reveal their essential roles in RNA processing. For example, knockout of SNRPB in cell lines leads to splicing defects and cell death, confirming its core function.
Point Mutation
Introducing point mutations in Sm or Lsm genes via CRISPR can model disease-associated variants. For instance, mutations in the Sm domain that impair RNA binding can be studied to understand their impact on splicing.
Knock-in
Knock-in of tagged versions of Sm or Lsm proteins (e.g., GFP) allows live-cell imaging and proteomic analysis. This approach can also be used to express disease-relevant mutants under endogenous regulation.
Overexpression
Overexpression of Lsm proteins using CRISPR activation or cDNA constructs can mimic cancer-associated upregulation and test oncogenic potential.
How EDITGENE Supports Sm-like protein family complex Research
Researchers studying Sm-like protein family complex-related genes often need to determine whether a candidate gene is causally involved in RNA processing or disease. EDITGENE provides comprehensive CRISPR-based services to facilitate these investigations, from knockout to knock-in and library screening.
Contact EDITGENE today to design your custom CRISPR model for Sm-like protein family complex research.
Frequently Asked Questions About Sm-like protein family complex
What is GO:0120114?
GO:0120114 is the Gene Ontology term for Sm-like protein family complex, a cellular component consisting of Sm and Lsm proteins that form RNA-binding rings [1, 2, 3].
What genes are involved in Sm-like protein family complex?
Key genes include SNRPB, SNRPD1, SNRPD2, SNRPD3, SNRPE, SNRPF, SNRPG, LSM1-8, and bacterial hfq [2, 6, 1].
What is the function of Sm-like protein family complex?
It functions in pre-mRNA splicing, mRNA decapping, and RNA degradation [2, 5, 7].
Where is Sm-like protein family complex located?
It is found in the nucleus (snRNPs) and cytoplasm (Lsm1-7) [2, 7].
What diseases are associated with Sm-like protein family complex?
Mutations are linked to cerebrocostomandibular syndrome, spinal muscular atrophy, cancer, and neurodegeneration [2, 6].
How can I study Sm-like protein family complex using CRISPR?
CRISPR knockout, knock-in, point mutation, and overexpression models can be used to dissect gene function [6, 7].
What is the structure of Sm-like protein family complex?
It typically forms hexameric or heptameric rings that bind RNA [2, 3].
Is Sm-like protein family complex conserved in bacteria?
Yes, Hfq is a bacterial Sm-like protein that mediates RNA-RNA interactions.
What are the subunits of Sm-like protein family complex?
Sm rings contain seven Sm proteins; Lsm rings contain Lsm1-7 or Lsm2-8 [2, 6].
How does Sm-like protein family complex bind RNA?
The Sm domain binds oligo(U) sequences with high specificity.
Conclusion
The Sm-like protein family complex (GO:0120114) is a fundamental cellular component with critical roles in RNA splicing, decay, and processing. Its evolutionary conservation and association with human diseases make it a compelling subject for research. CRISPR-based models and advanced methodologies offer powerful tools to unravel its mechanisms and therapeutic potential.
References
- 1. Møller T et al.. 2002. Hfq: a bacterial Sm-like protein that mediates RNA-RNA interaction.. Mol Cell 9(1):23-30 PMID: 11804583
- 2. Séraphin B. 1995. Sm and Sm-like proteins belong to a large family: identification of proteins of the U6 as well as the U1, U2, U4 and U5 snRNPs.. EMBO J 14(9):2089-98 PMID: 7744014
- 3. Salgado-Garrido J et al.. 1999. Sm and Sm-like proteins assemble in two related complexes of deep evolutionary origin.. EMBO J 18(12):3451-62 PMID: 10369684
- 4. Nielsen JS et al.. 2007. An Hfq-like protein in archaea: crystal structure and functional characterization of the Sm protein from Methanococcus jannaschii.. RNA 13(12):2213-23 PMID: 17959927
- 5. Wilusz CJ et al.. 2013. Lsm proteins and Hfq: Life at the 3' end.. RNA Biol 10(4):592-601 PMID: 23392247
- 6. Tharun S. 2009. Roles of eukaryotic Lsm proteins in the regulation of mRNA function.. Int Rev Cell Mol Biol 272:149-89 PMID: 19121818
- 7. Tharun S et al.. 2000. Yeast Sm-like proteins function in mRNA decapping and decay.. Nature 404(6777):515-8 PMID: 10761922
- 8. Achsel T et al.. 2001. The Sm domain is an ancient RNA-binding motif with oligo(U) specificity.. Proc Natl Acad Sci U S A 98(7):3685-9 PMID: 11259661
