GO:0031010 ISWI-type complex: Components, Assembly and Research Methods, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0031010 (ISWI-type complex) is a nuclear protein complex defined by an ATPase subunit of the imitation switch (ISWI) family that assembles chromatin and slides/spaces nucleosomes to regulate RNA polymerase I, II, and III transcription as well as DNA replication, recombination, and repair.
• ISWI-type complexes are conserved chromatin remodelers whose catalytic ATPase uses ATP hydrolysis to reposition nucleosomes, thereby controlling access to DNA.
• The composition of ISWI-type complexes determines their genomic location and function, with accessory subunits such as WSTF targeting the complex to replication sites and specific promoters.
• Post-translational modifications, including MAPK-dependent phosphorylation of WSTF, can switch cells between distinct ISWI-containing complexes, altering chromatin remodeling outcomes.
• ISWI-type complexes are implicated in developmental disorders and cancer through mutations in subunits or interacting proteins such as CHD7, although CHD7 belongs to a different remodeler family.
• Experimental dissection of ISWI-type complex function relies on knockout, point-mutation, knock-in, and overexpression cell models combined with chromatin accessibility and nucleosome positioning assays.
Description
The ISWI-type complex (GO:0031010) is a nuclear chromatin-remodeling machine defined by the presence of an ATPase subunit from the imitation switch (ISWI) family. These complexes are essential for organizing chromatin architecture and for sliding and spacing nucleosomes, thereby regulating transcription by nuclear RNA polymerases I, II, and III as well as DNA replication, recombination, and repair. Because nucleosome positioning controls access to genetic information, ISWI-type complexes sit at the heart of epigenetic regulation in eukaryotes. Researchers study ISWI-type complexes to understand how chromatin dynamics influence gene expression programs, cell-cycle progression, and genome stability. The functional diversity of ISWI-type complexes arises from their variable subunit composition, which directs them to specific genomic loci and biological processes. For example, the Williams syndrome transcription factor (WSTF) partners with ISWI ATPases to form distinct complexes that operate at replication sites and in transcription regulation. Phosphorylation of WSTF by MAPK can switch cells between different ISWI-containing complexes, illustrating how signaling pathways impinge on chromatin remodeling. Given their broad roles, ISWI-type complexes are attractive targets for understanding developmental disorders and cancers linked to chromatin dysregulation.
ISWI-type complex At A Glance
| GO ID | GO:0031010 |
|---|---|
| GO term | ISWI-type complex |
| Ontology | cellular_component |
| Synonym | None |
| Major function | ATP-dependent chromatin remodeling; nucleosome sliding and spacing; regulation of RNA polymerase I, II, and III transcription; DNA replication, recombination, and repair |
| Subunit composition | Contains an ISWI-family ATPase (e.g., Snf2h, Snf2l) plus accessory subunits such as WSTF, and other DDT-domain proteins |
| Cellular localization | Nucleus |
| Conservation | Evolutionarily conserved from yeast to humans |
| Related complexes | WSTF-ISWI complex, which functions at replication sites and in transcription |
What Is GO:0031010?
GO:0031010 (ISWI-type complex) is defined as any nuclear protein complex that contains an ATPase subunit of the imitation switch (ISWI) family. ISWI ATPases are involved in assembling chromatin and in sliding and spacing nucleosomes to regulate transcription of nuclear RNA polymerases I, II, and III and also DNA replication, recombination and repair.
Why Is ISWI-type complex Important in Cell Biology?
ISWI-type complexes are central to chromatin biology because they determine nucleosome positioning, which in turn controls DNA accessibility for transcription, replication, and repair. Their dysfunction is linked to developmental disorders and cancer, making them important for both basic research and therapeutic development. Understanding how ISWI-type complexes are targeted and regulated provides insight into epigenetic inheritance and genome stability.
• Regulate transcription by all three nuclear RNA polymerases through nucleosome sliding and spacing.
• Facilitate DNA replication by opening chromatin at replication sites, contributing to epigenetic inheritance.
• Participate in DNA recombination and repair by modulating chromatin accessibility.
• Their subunit composition determines genomic targeting and functional specificity.
• Post-translational modifications, such as WSTF phosphorylation, can switch between distinct ISWI complexes.
• Mutations in chromatin remodeler subunits, including ISWI-interacting proteins, are associated with human developmental disorders.
• ISWI-type complexes are potential targets for cancer therapy because of their roles in proliferation and genome stability.
• They serve as models for understanding ATP-dependent chromatin remodeling mechanisms.
• Nucleosome spacing by ISWI complexes affects higher-order chromatin structure.
• Experimental manipulation of ISWI subunits can reveal causal roles in specific cellular processes.
What Happens During ISWI-type complex?
Nucleosome sliding and spacing
In simple terms: ISWI complexes use energy to push nucleosomes along DNA, setting the spacing between them.
ISWI-type complexes hydrolyze ATP to slide nucleosomes along DNA, thereby establishing regular nucleosome spacing. This activity is critical for organizing chromatin into accessible and inaccessible regions, which influences transcription and other DNA transactions. The ISWI ATPase undergoes conformational changes upon ATP binding and hydrolysis that are coupled to template commitment and nucleosome movement.
Chromatin assembly
In simple terms: ISWI complexes help package DNA into chromatin by arranging nucleosomes correctly.
Beyond sliding, ISWI-type complexes participate in chromatin assembly, ensuring that newly synthesized DNA is properly wrapped into nucleosomes. This function is particularly important during DNA replication, where ISWI complexes at replication sites help maintain epigenetic information.
Regulation of transcription
In simple terms: By moving nucleosomes, ISWI complexes control whether genes can be turned on or off.
ISWI-type complexes regulate transcription by RNA polymerases I, II, and III through their effects on nucleosome positioning. For example, the WSTF-ISWI complex is involved in transcriptional regulation, and its distinct functions depend on the subunit composition. Phosphorylation of WSTF by MAPK can switch between different ISWI complexes, altering transcriptional outcomes.
DNA replication, recombination, and repair
In simple terms: ISWI complexes also help copy and repair DNA by making chromatin accessible.
ISWI ATPases are involved in DNA replication, recombination, and repair. At replication sites, the WSTF-ISWI complex opens chromatin to allow access to the replication machinery, providing a window for epigenetic inheritance. This function is essential for genome stability and for transmitting chromatin states to daughter cells.
Key Genes Involved in GO:0031010 ISWI-type complex
The following genes and proteins are key components or interactors of ISWI-type complexes, based on published literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| SMARCA5 (Snf2h) | ISWI-family ATPase catalytic subunit | Core catalytic engine of ISWI-type complexes; knockout causes chromatin defects |
| SMARCA1 (Snf2l) | ISWI-family ATPase catalytic subunit | Alternative ATPase in ISWI complexes; tissue-specific functions |
| BAZ1B (WSTF) | Accessory subunit of WSTF-ISWI complex | Targets ISWI to replication sites and regulates transcription; phosphorylation switches complexes |
| BAZ1A (ACF1) | Accessory subunit of ACF complex | Partners with ISWI ATPase for nucleosome spacing |
| BAZ2A (TIP5) | Accessory subunit of NoRC complex | Involved in rDNA silencing and nucleolar remodeling |
| CHD7 | Chromodomain helicase DNA-binding protein | Mutations impair chromatin remodeling and cause developmental disorders; not an ISWI subunit but related remodeler |
| DDT-domain proteins | Interact with SLIDE domain of ISWI | Mediate assembly of diverse ISWI complexes |
| H4K16ac | Histone modification | May influence ISWI complex recruitment |
| H3K4me3 | Histone modification | Associated with active chromatin and ISWI function |
| RNA polymerase I | Transcribes ribosomal RNA | Regulated by ISWI complexes at rDNA |
| RNA polymerase II | Transcribes protein-coding genes | Regulated by ISWI complexes |
| RNA polymerase III | Transcribes small RNAs | Regulated by ISWI complexes |
| MAPK | Kinase that phosphorylates WSTF | Regulates switching between ISWI complexes |
| Nucleosome | Basic unit of chromatin | Substrate for ISWI sliding and spacing |
| ATP | Energy source | Required for ISWI ATPase activity |
| DNA | Genetic material | Template for nucleosome sliding and repair |
| Replication machinery | DNA synthesis | Interacts with WSTF-ISWI at replication sites |
How Is ISWI-type complex Regulated?
ISWI-type complexes are regulated at multiple levels. Their subunit composition determines targeting and activity; for example, WSTF-ISWI and ACF-ISWI complexes have distinct functions despite sharing the ISWI ATPase. Post-translational modification of subunits, such as MAPK-mediated phosphorylation of WSTF, can switch cells between different ISWI-containing complexes, thereby altering chromatin remodeling outcomes. Additionally, the ATPase cycle itself is regulated by conformational changes that couple ATP binding and hydrolysis to nucleosome sliding. The availability of nucleosome substrates and histone modifications may also influence ISWI complex activity.
ISWI-type complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| BAZ1B (WSTF) | Williams syndrome; replication and transcription regulation | Knockout and point-mutation cell models to study complex switching |
| SMARCA5 (Snf2h) | Cancer; chromatin remodeling | Knockout and overexpression models to assess proliferation and genome stability |
| CHD7 | CHARGE syndrome; developmental disorder | Point-mutation knock-in to mimic patient mutations |
| SMARCA1 (Snf2l) | Neurodevelopment; chromatin regulation | Knockout and tagged knock-in for localization studies |
| BAZ1A (ACF1) | Cancer; nucleosome spacing | Knockout and rescue experiments |
Developmental disorders
Mutations in chromatin remodeling proteins, including CHD7, cause human developmental disorders such as CHARGE syndrome, and impair chromatin remodeling activity. Although CHD7 is not an ISWI subunit, this highlights the broader importance of remodeler function in development. ISWI-type complexes themselves are essential for proper chromatin organization during development.
Cancer
ISWI-type complexes regulate transcription, replication, and genome stability, processes that are frequently dysregulated in cancer. Their role in nucleosome spacing and chromatin accessibility can influence oncogene expression and DNA repair, making them potential therapeutic targets.
Williams syndrome
WSTF (BAZ1B) is implicated in Williams syndrome, a neurodevelopmental disorder. WSTF partners with ISWI ATPases to form distinct chromatin remodeling complexes, and its phosphorylation by MAPK regulates complex switching. This links ISWI-type complex regulation to neurological development.
From ISWI-type complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the catalytic role of ISWI ATPase in nucleosome sliding? | Knockout of SMARCA5/SMARCA1 with rescue by wild-type or ATPase-dead mutant |
| How does WSTF phosphorylation affect complex switching? | Point mutations in BAZ1B at MAPK phosphorylation sites |
| What is the effect of a disease-associated mutation in a remodeler? | Knock-in of patient mutations (e.g., CHD7) |
| Where and when are ISWI complexes localized? | Tagged knock-in of ISWI subunits with fluorescent tags |
| What happens when ISWI is overexpressed? | Overexpression cell models to study chromatin changes |
| Which genes are regulated by ISWI complexes? | Knockout followed by RNA-seq and ATAC-seq |
How to Study the ISWI-type complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| ATAC-seq | Chromatin accessibility | Assess nucleosome positioning changes after ISWI knockout |
| MNase-seq | Nucleosome spacing | Measure regular nucleosome arrays |
| RNA-seq | Gene expression | Identify transcriptional changes upon ISWI perturbation |
| ChIP-seq | Protein-DNA binding | Map ISWI subunit localization genome-wide |
| Co-IP/MS | Protein interactions | Determine ISWI complex composition |
| Live-cell imaging | Protein dynamics | Track ISWI at replication sites |
| In vitro remodeling assay | ATP-dependent nucleosome sliding | Study catalytic mechanism |
| Phospho-specific antibodies | WSTF phosphorylation | Monitor MAPK signaling to ISWI complexes |
Chromatin accessibility assays
ATAC-seq and MNase-seq measure nucleosome positioning and chromatin accessibility, which are directly affected by ISWI-type complex activity. These methods can reveal how knockout or mutation of ISWI subunits alters nucleosome spacing.
Transcription profiling
RNA-seq and nascent RNA labeling can quantify changes in RNA polymerase I, II, and III transcription upon manipulation of ISWI complexes. This helps identify target genes and pathways.
Protein interaction studies
Co-immunoprecipitation and mass spectrometry can identify subunits and interactors of ISWI complexes, such as WSTF and DDT-domain proteins. These approaches define complex composition and assembly.
Live-cell imaging
Fluorescent tagging of ISWI subunits allows tracking of complex localization and dynamics at replication sites and promoters. This provides spatial and temporal information.
How CRISPR Can Be Used to Study GO:0031010 ISWI-type complex
Knockout
CRISPR knockout of ISWI ATPase genes (SMARCA5, SMARCA1) or accessory subunits (BAZ1B, BAZ1A) can abolish complex function, leading to defects in nucleosome spacing, transcription, and replication. These models are essential for determining causality.
Point Mutation
Introducing point mutations in the ATPase domain of ISWI or in phosphorylation sites of WSTF (BAZ1B) allows dissection of catalytic and regulatory mechanisms without deleting the protein. For example, ATPase-dead mutants can separate ATP hydrolysis from nucleosome binding.
Knock-in
Knock-in of tagged ISWI subunits (e.g., GFP or HA) enables localization and interaction studies in a physiological context. Disease-associated mutations, such as those in CHD7, can also be knocked in to model developmental disorders.
Overexpression
Overexpression of ISWI subunits or accessory proteins can reveal dominant effects on chromatin structure and transcription. This is useful for studying gain-of-function mechanisms in cancer.
How EDITGENE Supports ISWI-type complex Research
Researchers studying ISWI-type complex-related genes often need to determine whether a candidate gene is causally involved in chromatin remodeling, transcription regulation, or disease. EDITGENE provides tailored CRISPR cell models and screening services to accelerate this discovery.
Contact EDITGENE today to design your custom CRISPR model for ISWI-type complex research.
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Frequently Asked Questions About ISWI-type complex
What is GO:0031010?
GO:0031010 is the Gene Ontology term for ISWI-type complex, a nuclear protein complex containing an ISWI-family ATPase that remodels chromatin by sliding and spacing nucleosomes.
What genes are involved in ISWI-type complex?
Key genes include SMARCA5 (Snf2h), SMARCA1 (Snf2l), BAZ1B (WSTF), BAZ1A (ACF1), and BAZ2A (TIP5), among others.
What is the function of ISWI-type complex?
It assembles chromatin and slides/spaces nucleosomes to regulate transcription by RNA polymerases I, II, and III, as well as DNA replication, recombination, and repair.
Where is ISWI-type complex located?
It is a nuclear protein complex.
How is ISWI-type complex regulated?
Regulation occurs through subunit composition and post-translational modifications such as MAPK-mediated phosphorylation of WSTF, which switches between distinct complexes.
What diseases are associated with ISWI-type complex?
Dysregulation is linked to developmental disorders, cancer, and Williams syndrome through subunits like WSTF and related remodelers.
What methods are used to study ISWI-type complex?
Common methods include ATAC-seq, MNase-seq, RNA-seq, ChIP-seq, co-immunoprecipitation, and live-cell imaging.
Can CRISPR be used to study ISWI-type complex?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are widely used to dissect ISWI complex function.
What is the role of WSTF in ISWI-type complex?
WSTF (BAZ1B) is an accessory subunit that targets ISWI to replication sites and regulates transcription; its phosphorylation by MAPK switches complex composition.
Why is ISWI-type complex important for research?
It is central to chromatin dynamics, epigenetic inheritance, and genome stability, making it relevant to development and disease.
Conclusion
ISWI-type complexes (GO:0031010) are essential ATP-dependent chromatin remodelers that control nucleosome positioning and thereby influence transcription, replication, recombination, and repair. Their diverse subunit composition and regulation by signaling pathways allow them to carry out specialized functions in the nucleus. Understanding these complexes provides insight into epigenetic mechanisms and offers potential avenues for therapeutic intervention in developmental disorders and cancer. Continued research using advanced CRISPR models and genomic assays will further elucidate their roles in health and disease.
References
- 1. Erdel F et al.. 2011. Chromatin remodelling in mammalian cells by ISWI-type complexes--where, when and why?. FEBS J 278(19):3608-18 PMID: 21810179
- 2. Poot RA et al.. 2005. Chromatin remodeling by WSTF-ISWI at the replication site: opening a window of opportunity for epigenetic inheritance?. Cell Cycle 4(4):543-6 PMID: 15753658
- 3. Gangaraju VK et al.. 2009. Conformational changes associated with template commitment in ATP-dependent chromatin remodeling by ISW2.. Mol Cell 35(1):58-69 PMID: 19595716
- 4. Prasad P et al.. 2010. Control of nucleosome movement: to space or not to space nucleosomes?. Epigenetics 5(4):282-6 PMID: 20421732
- 5. Yoshimura K et al.. 2009. Distinct function of 2 chromatin remodeling complexes that share a common subunit, Williams syndrome transcription factor (WSTF).. Proc Natl Acad Sci U S A 106(23):9280-5 PMID: 19470456
- 6. Dong J et al.. 2013. SLIDE, the protein interacting domain of Imitation Switch remodelers, binds DDT-domain proteins of different subfamilies in chromatin remodeling complexes.. J Integr Plant Biol 55(10):928-37 PMID: 23691993
- 7. Bouazoune K et al.. 2012. Chromatin remodeling by the CHD7 protein is impaired by mutations that cause human developmental disorders.. Proc Natl Acad Sci U S A 109(47):19238-43 PMID: 23134727
- 8. Oya H et al.. 2009. Phosphorylation of Williams syndrome transcription factor by MAPK induces a switching between two distinct chromatin remodeling complexes.. J Biol Chem 284(47):32472-82 PMID: 19776015
