GO:0071339 MLL1 complex: Components, Assembly and Research Methods, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0071339 (MLL1 complex) is a histone H3 lysine-4 (H3K4) methyltransferase complex whose catalytic subunit is MLL1/MLL (KMT2A), together with core components ASH2L, HCFC1/HCF1, WDR5 and RBBP5.
• The complex is a key epigenetic regulator of gene expression, and its activity is linked to leukemogenesis and to the control of fetal hemoglobin.
• Menin-MLL1 interaction is a molecular dependency in NUP98-rearranged AML and in mutant NPM1 AML, making the complex a therapeutic target.
• The MLL1-WRAD complex binds H2B-ubiquitinated nucleosomes and adopts multiple structural states, coupling ubiquitin signaling to H3K4 methylation.
• MLL1 complex activity can be studied by knockout, point-mutation, knock-in and overexpression cell models, combined with CRISPR library screening and bioinformatics.
• Dysregulation of the MLL1 complex is implicated in hepatocellular carcinoma survival and in epigenetic therapy resistance.
Description
The MLL1 complex (GO:0071339) is a cellular component defined as a protein complex that can methylate lysine-4 of histone H3, with MLL1/MLL as the catalytic methyltransferase subunit and ASH2L, HCFC1/HCF1, WDR5 and RBBP5 as core components. This complex is a central epigenetic regulator that writes the H3K4me mark, a modification associated with active transcription, and its dysfunction is linked to hematological malignancies and other cancers. Because the complex controls gene expression programs, researchers study it to understand leukemogenesis, fetal hemoglobin regulation and epigenetic therapy responses. The MLL1 complex is also a target for small-molecule inhibitors that disrupt its interaction with menin, a dependency in NUP98-rearranged AML and mutant NPM1 AML. Understanding its composition, assembly and regulation is therefore essential for both basic chromatin biology and translational oncology.
MLL1 complex At A Glance
| GO ID | GO:0071339 |
|---|---|
| GO term | MLL1 complex |
| Ontology | cellular_component |
| Synonym | None |
| Major function | Histone H3 lysine-4 methylation |
| Catalytic subunit | MLL1/MLL (KMT2A) |
| Core components | ASH2L, HCFC1/HCF1, WDR5, RBBP5 |
| Associated complex | WRAD (WDR5, RBBP5, ASH2L, DPY30) |
| Disease relevance | Leukemogenesis, hepatocellular carcinoma, fetal hemoglobin regulation |
What Is GO:0071339?
GO:0071339 (MLL1 complex) is a protein complex that can methylate lysine-4 of histone H3. MLL1/MLL is the catalytic methyltransferase subunit, and the complex also contains the core components ASH2L, HCFC1/HCF1, WDR5 and RBBP5. This complex functions as an epigenetic writer that deposits H3K4 methylation marks, thereby influencing transcription.
Why Is MLL1 complex Important in Cell Biology?
The MLL1 complex is important because it is a master epigenetic regulator that controls gene expression through H3K4 methylation, and its dysregulation is directly implicated in leukemogenesis and other cancers. The menin-MLL1 interaction is a molecular dependency in NUP98-rearranged AML and mutant NPM1 AML, making the complex a validated therapeutic target. In addition, the MLL1 complex inhibits fetal hemoglobin expression, linking it to hemoglobin switching and potential therapies for hemoglobinopathies. Epigenetic therapies targeting histone lysine methylation face complex mechanisms and clinical challenges, underscoring the need to understand MLL1 complex biology.
• The MLL1 complex is a key writer of H3K4 methylation, a mark of active transcription.
• MLL1/WDR5 complex is directly involved in leukemogenesis and epigenetic regulation.
• Menin-MLL1 interaction is a molecular dependency in NUP98-rearranged AML.
• Mutant NPM1 directly regulates oncogenic transcription through the MLL1 complex in AML.
• The MLL1 complex inhibits fetal hemoglobin expression, linking it to hemoglobin switching.
• Menin-MLL1 complex cooperates with NF-Y to promote hepatocellular carcinoma survival.
• Epigenetic therapies targeting histone lysine methylation face complex mechanisms and clinical challenges.
• The MLL1-WRAD complex binds H2B-ubiquitinated nucleosomes, coupling ubiquitin signaling to methylation.
• The complex is a target for small-molecule inhibitors that disrupt menin-MLL1 binding.
• Understanding MLL1 complex assembly aids in designing CRISPR-based disease models.
Structure and Composition of MLL1 complex
Catalytic subunit MLL1/MLL (KMT2A)
In simple terms: MLL1 is the enzyme that actually adds the methyl mark to histone H3.
MLL1/MLL (KMT2A) is the catalytic methyltransferase subunit of the MLL1 complex, responsible for methylating lysine-4 of histone H3. Its activity is essential for the complex's epigenetic function, and its dysregulation is linked to leukemogenesis.
Core component WDR5
In simple terms: WDR5 is a scaffold protein that helps assemble the complex and present the histone substrate.
WDR5 is a core component of the MLL1 complex and is part of the WRAD subcomplex (WDR5, RBBP5, ASH2L, DPY30) that stimulates MLL1 methyltransferase activity. The MLL1/WDR5 complex is directly implicated in leukemogenesis and epigenetic regulation.
Core component RBBP5
In simple terms: RBBP5 is a regulatory subunit that helps the complex methylate histones efficiently.
RBBP5 is a core component of the MLL1 complex and part of the WRAD subcomplex that enhances MLL1 catalytic activity. Structural studies of the MLL1-WRAD complex bound to H2B-ubiquitinated nucleosomes reveal multiple states that coordinate substrate recognition.
Core component ASH2L
In simple terms: ASH2L is a structural platform that holds the complex together.
ASH2L is a core component of the MLL1 complex and a member of the WRAD subcomplex. It contributes to the assembly and stability of the complex, which is required for H3K4 methylation.
Core component HCFC1/HCF1
In simple terms: HCFC1 is a host cell factor that helps regulate the complex's activity.
HCFC1/HCF1 is listed as a core component of the MLL1 complex in the GO definition. It is thought to modulate the complex's function in transcription and epigenetic regulation.
Assembly and multistate conformations
In simple terms: The complex can change shape to read different histone signals.
The MLL1-WRAD complex adopts multistate structures when bound to H2B-ubiquitinated nucleosomes, coupling ubiquitin signaling to H3K4 methylation. This structural plasticity is important for its regulation and for designing inhibitors.
Key Genes Involved in GO:0071339 MLL1 complex
The following genes and proteins are key components or regulators of the MLL1 complex (GO:0071339).
| Gene | Major Role | Research Relevance |
|---|---|---|
| KMT2A (MLL1) | Catalytic H3K4 methyltransferase subunit | Leukemogenesis, epigenetic regulation |
| WDR5 | Core scaffold, part of WRAD | MLL1/WDR5 complex in leukemogenesis |
| RBBP5 | Core regulatory subunit, part of WRAD | Stimulates MLL1 activity |
| ASH2L | Core structural subunit, part of WRAD | Complex assembly and stability |
| HCFC1 (HCF1) | Core component | Modulates complex function |
| DPY30 | WRAD component | Enhances methyltransferase activity |
| MEN1 (Menin) | Interacts with MLL1 | Molecular dependency in NUP98-rearranged AML |
| NPM1 | Mutant NPM1 regulates oncogenic transcription | AML pathogenesis |
| NUP98 | Fusion partner in NUP98-rearranged AML | Menin-MLL1 dependency |
| NF-Y | Cooperates with Menin-MLL1 | Hepatocellular carcinoma survival |
| HBB | Fetal hemoglobin target gene | MLL1 complex inhibits fetal hemoglobin |
| HBG1/HBG2 | Fetal hemoglobin genes | Regulated by MLL1 complex |
| KMT2B (MLL2) | Related H3K4 methyltransferase | Epigenetic regulation |
| KMT2C (MLL3) | Related H3K4 methyltransferase | Epigenetic regulation |
| KMT2D (MLL4) | Related H3K4 methyltransferase | Epigenetic regulation |
| SETD1A | Related H3K4 methyltransferase | Epigenetic regulation |
| SETD1B | Related H3K4 methyltransferase | Epigenetic regulation |
How Is MLL1 complex Regulated?
The MLL1 complex is regulated by its interaction with menin (MEN1), which is a molecular dependency in NUP98-rearranged AML and mutant NPM1 AML. The complex also cooperates with transcription factors such as NF-Y to promote hepatocellular carcinoma survival. Its activity is further modulated by H2B ubiquitination, which influences the multistate conformations of the MLL1-WRAD complex. Epigenetic therapies targeting histone lysine methylation can affect MLL1 complex function, though clinical challenges remain.
MLL1 complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| KMT2A (MLL1) | Leukemogenesis | Knockout AML cell lines |
| MEN1 | NUP98-rearranged AML | Point mutation of menin binding site |
| NPM1 | Mutant NPM1 AML | Knock-in of NPM1 mutation |
| NF-Y | Hepatocellular carcinoma | Knockout HCC cell lines |
| HBB | Fetal hemoglobin regulation | Overexpression of MLL1 complex |
MLL1 complex in leukemia
The MLL1/WDR5 complex is directly involved in leukemogenesis and epigenetic regulation. Menin-MLL1 interaction is a molecular dependency in NUP98-rearranged AML, and mutant NPM1 directly regulates oncogenic transcription in AML through this complex. These findings make the MLL1 complex a therapeutic target in acute myeloid leukemia.
MLL1 complex in hepatocellular carcinoma
Menin-MLL1 complex cooperates with NF-Y to promote hepatocellular carcinoma survival, indicating that the complex supports tumor cell viability in liver cancer. Targeting this interaction may offer a strategy for hepatocellular carcinoma therapy.
MLL1 complex and fetal hemoglobin regulation
The histone methyltransferase MLL1 complex inhibits expression of fetal hemoglobin, linking it to hemoglobin switching. This suggests that modulating the complex could be explored for hemoglobinopathies.
Epigenetic therapy challenges
Epigenetic therapies targeting histone lysine methylation, including the MLL1 complex, face complex mechanisms and clinical challenges. Understanding these mechanisms is critical for developing effective treatments.
From MLL1 complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of MLL1 complex reduce H3K4 methylation? | Knockout of KMT2A or WDR5 |
| Does menin-MLL1 interaction drive AML? | Point mutation of MEN1 binding interface |
| Does mutant NPM1 require MLL1 complex? | Knock-in of NPM1 mutation |
| Does MLL1 complex regulate fetal hemoglobin? | Overexpression of MLL1 complex |
| Does NF-Y cooperate with Menin-MLL1 in HCC? | Knockout of NF-Y subunits |
| Can epigenetic inhibitors target MLL1 complex? | Tagged knock-in for drug screening |
How to Study the MLL1 complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| CRISPR knockout screen | Gene dependencies | Identify MLL1 complex vulnerabilities |
| ChIP-seq | Genomic binding of H3K4me and MLL1 | Map target genes |
| Cryo-EM | 3D structure of MLL1-WRAD | Understand multistate conformations |
| Mass spectrometry | Protein interactions and modifications | Identify complex components |
| RT-qPCR | Fetal hemoglobin mRNA | Assess MLL1 complex regulation |
| Flow cytometry | Fetal hemoglobin protein | Quantify hemoglobin switching |
| Drug sensitivity assays | Response to menin-MLL1 inhibitors | Evaluate therapeutic targeting |
CRISPR knockout screening
CRISPR knockout screens can identify genes required for MLL1 complex function and for leukemia cell survival. Such screens help uncover dependencies like menin-MLL1 in NUP98-rearranged AML.
Chromatin immunoprecipitation and sequencing
ChIP-seq for H3K4 methylation and MLL1 complex components reveals genomic binding sites and target genes. This method is used to study how the complex regulates transcription.
Structural biology and proteomics
Cryo-EM and mass spectrometry have revealed multistate structures of the MLL1-WRAD complex bound to H2B-ubiquitinated nucleosomes. Proteomics can identify complex components and post-translational modifications.
Functional assays for fetal hemoglobin
Fetal hemoglobin expression can be measured by RT-qPCR and flow cytometry after manipulating the MLL1 complex. This links the complex to hemoglobin switching.
How CRISPR Can Be Used to Study GO:0071339 MLL1 complex
Knockout
CRISPR knockout of KMT2A, WDR5, RBBP5, ASH2L or HCFC1 can abolish MLL1 complex function and reduce H3K4 methylation. Such models are used to study leukemogenesis and to validate therapeutic targets.
Point Mutation
Point mutations can be introduced into the menin-binding interface of MLL1 to disrupt the menin-MLL1 interaction, mimicking small-molecule inhibition. This helps test the dependency of NUP98-rearranged AML on this interaction.
Knock-in
Knock-in of mutant NPM1 or of tagged MLL1 complex components allows tracking of oncogenic transcription and complex localization. Tagged knock-in can also facilitate drug screening.
Overexpression
Overexpression of MLL1 complex components can be used to study fetal hemoglobin repression and to identify downstream targets. It also helps assess gain-of-function effects in cancer models.
How EDITGENE Supports MLL1 complex Research
Researchers studying MLL1 complex-related genes often need to determine whether a candidate gene is causally involved in H3K4 methylation, leukemogenesis or fetal hemoglobin regulation. EDITGENE provides CRISPR-based cell model services to enable such functional studies with high precision and reproducibility.
Contact EDITGENE today to design your custom CRISPR model for MLL1 complex research.
Frequently Asked Questions About MLL1 complex
What is the MLL1 complex?
The MLL1 complex (GO:0071339) is a protein complex that methylates lysine-4 of histone H3, with MLL1/MLL as the catalytic subunit and ASH2L, HCFC1/HCF1, WDR5 and RBBP5 as core components.
What genes are involved in the MLL1 complex?
Key genes include KMT2A (MLL1), WDR5, RBBP5, ASH2L, HCFC1, and DPY30, as well as interactors like MEN1 and NPM1.
What is the function of GO:0071339?
GO:0071339 describes a histone H3K4 methyltransferase complex that regulates transcription and is implicated in leukemogenesis and fetal hemoglobin regulation.
How is the MLL1 complex linked to leukemia?
The MLL1/WDR5 complex is involved in leukemogenesis, and menin-MLL1 interaction is a dependency in NUP98-rearranged AML and mutant NPM1 AML.
What diseases are associated with MLL1 complex mutations?
Dysregulation of the MLL1 complex is associated with acute myeloid leukemia, hepatocellular carcinoma and altered fetal hemoglobin expression.
How can I study the MLL1 complex in the lab?
Common methods include CRISPR knockout, ChIP-seq, cryo-EM, proteomics and fetal hemoglobin assays.
What is the role of WDR5 in the MLL1 complex?
WDR5 is a core scaffold component that helps assemble the complex and stimulate MLL1 methyltransferase activity.
Does the MLL1 complex regulate fetal hemoglobin?
Yes, the histone methyltransferase MLL1 complex inhibits expression of fetal hemoglobin.
What are the therapeutic implications of targeting the MLL1 complex?
Targeting menin-MLL1 interaction is a promising strategy in AML, and epigenetic therapies targeting histone lysine methylation are under investigation.
What CRISPR models are available for MLL1 complex research?
Knockout, point mutation, knock-in and overexpression models can be generated for MLL1 complex genes to study function and disease.
Conclusion
The MLL1 complex (GO:0071339) is a central epigenetic regulator that methylates histone H3 lysine-4 and controls gene expression programs relevant to leukemia, hepatocellular carcinoma and fetal hemoglobin regulation. Its core components, including MLL1, WDR5, RBBP5, ASH2L and HCFC1, form a dynamic machine whose structural states and interactions are critical for function. Targeting the complex, particularly the menin-MLL1 interaction, represents a promising therapeutic avenue. Continued research using CRISPR models and bioinformatics will further elucidate its roles and vulnerabilities.
References
- 1. Dzama-Karels M et al.. 2025. Menin-MLL1 complex cooperates with NF-Y to promote hepatocellular carcinoma survival.. Cell Rep 44(12):116619 PMID: 41296561
- 3. Wu M et al.. 2011. MLL1/WDR5 complex in leukemogenesis and epigenetic regulation.. Chin J Cancer 30(4):240-6 PMID: 21439245
- 4. Heikamp EB et al.. 2022. The menin-MLL1 interaction is a molecular dependency in NUP98-rearranged AML.. Blood 139(6):894-906 PMID: 34582559
- 5. Rahman S et al.. 2022. Multistate structures of the MLL1-WRAD complex bound to H2B-ubiquitinated nucleosome.. Proc Natl Acad Sci U S A 119(38):e2205691119 PMID: 36095189
- 6. Uckelmann HJ et al.. 2023. Mutant NPM1 Directly Regulates Oncogenic Transcription in Acute Myeloid Leukemia.. Cancer Discov 13(3):746-765 PMID: 36455613
- 7. Gold S et al.. 2024. Epigenetic therapies targeting histone lysine methylation: complex mechanisms and clinical challenges.. J Clin Invest 134(20) PMID: 39403928
- 8. Han Y et al.. 2025. The histone methyltransferase MLL1 complex inhibits expression of fetal hemoglobin.. J Biol Chem 301(12):110863 PMID: 41161385
