GO:0141000 histone H4K91 ubiquitin ligase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0141000 defines the molecular function of catalyzing ubiquitin transfer to histone H4 at lysine 91 (H4K91).
• This activity is mediated by the B-lymphoma and BAL-associated protein (BBAP), also known as DTX3L, an E3 ubiquitin ligase.
• H4K91 ubiquitination by BBAP is required for the recruitment of DNA repair factors such as 53BP1 to sites of DNA damage.
• Loss of BBAP-mediated H4K91 ubiquitination impairs DNA double-strand break repair and confers sensitivity to chemotherapeutic agents.
• The activity is regulated by histone deacetylases HDAC1 and HDAC2, which are required for BBAP function in DNA repair.
• Studying GO:0141000 helps researchers understand chromatin-based DNA damage responses and develop strategies to overcome chemoresistance in lymphoma.
Description
Histone proteins are subject to a wide array of post-translational modifications that regulate chromatin structure and function. Among these, ubiquitination of histone H4 at lysine 91 (H4K91) has emerged as a critical modification for DNA damage signaling and repair. The enzyme responsible for this specific modification is BBAP (B-lymphoma and BAL-associated protein), also known as DTX3L, which functions as an E3 ubiquitin ligase. The Gene Ontology term GO:0141000, histone H4K91 ubiquitin ligase activity, captures this precise molecular function. Understanding this activity is essential for researchers studying chromatin dynamics, DNA repair, and cancer biology, as it provides a direct link between histone modification and genome stability.
histone H4K91 ubiquitin ligase activity At A Glance
| GO ID | GO:0141000 |
|---|---|
| GO term | histone H4K91 ubiquitin ligase activity |
| Ontology | molecular_function |
| Synonym | histone H4-K91 ubiquitin ligase activity; histone ubiquitin ligase activity (H4-K91 specific) |
| Major function | Catalyzes ubiquitin transfer to histone H4 at lysine 91 |
| Substrate | Histone H4 (at K91) |
| Product | Ubiquitinated histone H4 (H4K91ub) |
| Enzyme class | E3 ubiquitin ligase |
| Key enzyme | BBAP (DTX3L) |
| Regulatory proteins | HDAC1, HDAC2 |
| Associated process | DNA double-strand break repair |
What Is GO:0141000?
GO:0141000, histone H4K91 ubiquitin ligase activity, is a molecular function defined as the catalysis of the transfer of a ubiquitin molecule to histone 4 at the lysine-91 residue. In other words, it is the enzymatic activity that attaches a single ubiquitin moiety to a specific lysine on histone H4, a modification that can alter chromatin structure and recruit downstream factors. This activity is distinct from other ubiquitin ligase functions due to its strict substrate specificity for histone H4 at K91.
Why Is histone H4K91 ubiquitin ligase activity Important in Cell Biology?
GO:0141000 is important because it represents a specific chromatin modification that is essential for the DNA damage response. The ubiquitination of histone H4 at K91 by BBAP creates a docking site for the recruitment of DNA repair proteins, including 53BP1, to sites of DNA double-strand breaks. This activity is critical for maintaining genomic integrity, and its dysregulation has been implicated in cancer, particularly in diffuse large B-cell lymphoma (DLBCL), where EZH2 gain-of-function mutations and HDAC1/2 inhibition affect BBAP-mediated repair. Thus, understanding this molecular function provides insights into chemoresistance and potential therapeutic targets.
• Required for efficient DNA double-strand break repair via recruitment of 53BP1.
• Links histone ubiquitination to chromatin remodeling and DNA damage signaling.
• Implicated in diffuse large B-cell lymphoma (DLBCL) pathogenesis and chemoresistance.
• Regulated by HDAC1 and HDAC2, connecting acetylation and ubiquitination pathways.
• Potential biomarker for sensitivity to DNA-damaging chemotherapies.
• Target for overcoming EZH2 gain-of-function mutant DLBCL chemoresistance.
• Provides a model for studying crosstalk between histone modifications.
• Essential for understanding how chromatin context influences DNA repair.
• May inform development of combination therapies with HDAC inhibitors.
• Highlights the importance of E3 ligases in genome stability.
Molecular Mechanism of histone H4K91 ubiquitin ligase activity
Substrate Recognition and Binding
In simple terms: The enzyme first finds and grabs onto the histone protein it needs to modify.
BBAP (DTX3L) specifically recognizes histone H4, likely through its substrate-binding domains, and positions the lysine 91 residue for ubiquitin transfer. This specificity ensures that only H4K91 is modified, distinguishing it from other histone ubiquitination events.
Catalytic Transfer of Ubiquitin
In simple terms: The enzyme attaches a ubiquitin molecule onto the histone.
BBAP functions as an E3 ubiquitin ligase, facilitating the transfer of ubiquitin from an E2 conjugating enzyme to the epsilon-amino group of lysine 91 on histone H4. This reaction results in a covalent isopeptide bond between ubiquitin and H4K91.
Role in DNA Damage Response
In simple terms: The ubiquitin tag acts as a signal for DNA repair machinery to come to damaged sites.
Upon DNA double-strand breaks, H4K91 ubiquitination by BBAP is required for the recruitment of 53BP1 and other repair factors to damage sites. This step is critical for non-homologous end joining and homologous recombination repair pathways.
Regulation by HDAC1 and HDAC2
In simple terms: Other enzymes can control whether this ubiquitination happens.
HDAC1 and HDAC2 are required for BBAP-mediated H4K91 ubiquitination and subsequent DNA repair. Inhibition of HDAC1/2 impairs this process, leading to defective repair and increased chemosensitivity in certain lymphomas.
Crosstalk with Other Histone Modifications
In simple terms: This modification can affect or be affected by other chemical tags on histones.
H4K91 ubiquitination may influence or be influenced by other histone modifications such as acetylation and methylation, contributing to a complex regulatory network that fine-tunes chromatin structure and DNA repair.
Key Genes Involved in GO:0141000 histone H4K91 ubiquitin ligase activity
The following genes and proteins are directly involved in or regulate histone H4K91 ubiquitin ligase activity.
| Gene | Major Role | Research Relevance |
|---|---|---|
| DTX3L (BBAP) | E3 ubiquitin ligase that catalyzes H4K91 ubiquitination | Core enzyme; target for modulating DNA repair |
| H4C1-H4C16 | Histone H4 variants; substrate for ubiquitination at K91 | Substrate specificity and chromatin studies |
| HDAC1 | Histone deacetylase; required for BBAP-mediated repair | Regulator; HDAC inhibitors affect H4K91ub |
| HDAC2 | Histone deacetylase; required for BBAP-mediated repair | Regulator; HDAC inhibitors affect H4K91ub |
| TP53BP1 | DNA repair protein recruited by H4K91ub | Downstream effector; marker of repair |
| EZH2 | Histone methyltransferase; gain-of-function mutations affect repair | Context-dependent; chemoresistance |
| UBE2D1 | E2 ubiquitin-conjugating enzyme | Potential partner for ubiquitin transfer |
| UBE2D2 | E2 ubiquitin-conjugating enzyme | Potential partner for ubiquitin transfer |
| UBE2D3 | E2 ubiquitin-conjugating enzyme | Potential partner for ubiquitin transfer |
| UBE2N | E2 ubiquitin-conjugating enzyme | Potential partner for ubiquitin transfer |
| RNF8 | E3 ubiquitin ligase in DNA damage response | May cooperate with BBAP |
| RNF168 | E3 ubiquitin ligase in DNA damage response | May cooperate with BBAP |
| ATM | DNA damage kinase; upstream of repair | Regulates damage response |
| ATR | DNA damage kinase; upstream of repair | Regulates damage response |
| MDC1 | Mediator of DNA damage checkpoint | Facilitates repair factor recruitment |
| H2AX | Histone variant; phosphorylated at damage sites | Marker of DNA damage |
| BRCA1 | Homologous recombination repair | Potential crosstalk with H4K91ub |
| 53BP1 | DNA repair factor | Recruited by H4K91ub |
How Is histone H4K91 ubiquitin ligase activity Regulated?
The activity of histone H4K91 ubiquitin ligase is regulated by HDAC1 and HDAC2, which are required for BBAP-mediated DNA repair. Inhibition of HDAC1/2 impairs H4K91 ubiquitination and sensitizes cells to DNA-damaging agents. Additionally, EZH2 gain-of-function mutations can affect this pathway, contributing to chemoresistance in diffuse large B-cell lymphoma.
histone H4K91 ubiquitin ligase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| DTX3L (BBAP) | DLBCL, chemoresistance | Knockout in lymphoma cell lines |
| HDAC1 | DLBCL, chemoresistance | Knockout or inhibitor treatment |
| HDAC2 | DLBCL, chemoresistance | Knockout or inhibitor treatment |
| EZH2 | DLBCL, chemoresistance | Point mutation (gain-of-function) |
| TP53BP1 | DNA repair deficiency | Knockout in cancer cell lines |
Diffuse Large B-Cell Lymphoma (DLBCL)
In DLBCL, EZH2 gain-of-function mutations and HDAC1/2 inhibition impair BBAP-mediated H4K91 ubiquitination, leading to defective DNA repair and chemoresistance. Targeting this pathway may overcome resistance to chemotherapy.
Chemoresistance in Cancer
Loss of H4K91 ubiquitination due to BBAP dysfunction or HDAC inhibition reduces DNA repair capacity, which can be exploited to sensitize tumors to DNA-damaging agents. Conversely, upregulation may contribute to resistance.
Genomic Instability Disorders
Defects in H4K91 ubiquitination could lead to genomic instability, a hallmark of cancer and certain developmental disorders, though direct evidence in non-lymphoma contexts requires further study.
From histone H4K91 ubiquitin ligase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of DTX3L impair H4K91 ubiquitination? | DTX3L knockout cell line |
| Does HDAC inhibition affect H4K91ub? | HDAC1/2 knockout or inhibitor-treated cells |
| Does EZH2 mutation alter H4K91ub? | EZH2 point-mutation knock-in |
| Can H4K91ub be detected in vivo? | Tagged knock-in of H4K91 (e.g., HA-ubiquitin) |
| Does overexpression of BBAP enhance repair? | DTX3L overexpression |
| What proteins are recruited by H4K91ub? | Knock-in of H4K91R mutant |
How to Study the histone H4K91 ubiquitin ligase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Western blot | Protein levels of H4K91ub | Assessing modification status |
| Mass spectrometry | Precise site of ubiquitination | Confirming H4K91 specificity |
| Comet assay | DNA damage and repair capacity | Functional impact of H4K91ub |
| Gamma-H2AX foci | DNA double-strand breaks | Repair kinetics |
| ChIP | Localization of H4K91ub on chromatin | Mapping at damage sites |
| CRISPR knockout screen | Genes required for H4K91ub | Identifying regulators |
| Immunoprecipitation | Protein interactions with BBAP | Finding E2 partners |
| RNA-seq | Transcriptional changes upon loss of H4K91ub | Downstream effects |
Detection of H4K91 Ubiquitination
Western blotting with antibodies specific to ubiquitinated H4K91 can measure the modification level. Mass spectrometry can confirm the precise site of ubiquitination.
DNA Repair Assays
Comet assays, gamma-H2AX foci formation, and 53BP1 recruitment assays can assess the functional impact of H4K91 ubiquitination on DNA repair.
Chromatin Immunoprecipitation (ChIP)
ChIP with anti-ubiquitin or anti-H4K91ub antibodies can determine the localization of this modification at DNA damage sites.
CRISPR Screens
Genome-wide CRISPR knockout screens can identify genes that regulate or depend on H4K91 ubiquitination, such as E2 enzymes or repair factors.
How CRISPR Can Be Used to Study GO:0141000 histone H4K91 ubiquitin ligase activity
Knockout
CRISPR knockout of DTX3L (BBAP) can abolish H4K91 ubiquitination, allowing researchers to study its role in DNA repair and chemosensitivity. Knockout of HDAC1/2 can also impair this activity.
Point Mutation
Introducing point mutations in DTX3L to disrupt its catalytic activity or in histone H4 at K91 (K91R) can specifically abolish ubiquitination without affecting other functions, providing precise mechanistic insights.
Knock-in
Knock-in of tagged ubiquitin or H4K91 mutants can enable visualization and tracking of H4K91 ubiquitination in live cells, facilitating dynamic studies.
Overexpression
Overexpression of DTX3L can enhance H4K91 ubiquitination and DNA repair, useful for gain-of-function studies and testing chemoresistance mechanisms.
How EDITGENE Supports histone H4K91 ubiquitin ligase activity Research
Researchers studying histone H4K91 ubiquitin ligase activity-related genes often need to determine whether a candidate gene is causally involved in DNA repair, chromatin regulation, or chemoresistance. EDITGENE provides comprehensive CRISPR-based services to generate precisely engineered cell models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for histone H4K91 ubiquitin ligase activity research.
Frequently Asked Questions About histone H4K91 ubiquitin ligase activity
What is histone H4K91 ubiquitin ligase activity?
It is the enzymatic activity that attaches a ubiquitin molecule to histone H4 at lysine 91, a modification important for DNA repair.
What gene encodes the enzyme for H4K91 ubiquitination?
The enzyme is BBAP, encoded by the DTX3L gene.
What is the role of H4K91 ubiquitination in DNA repair?
It recruits repair factors like 53BP1 to DNA double-strand breaks, facilitating repair.
How is H4K91 ubiquitination regulated?
It is regulated by HDAC1 and HDAC2, and affected by EZH2 mutations in lymphoma.
What diseases are associated with H4K91 ubiquitin ligase activity?
Diffuse large B-cell lymphoma and chemoresistance are linked to defects in this pathway.
What methods are used to study H4K91 ubiquitination?
Western blot, mass spectrometry, ChIP, and CRISPR screens are commonly used.
Can CRISPR be used to study H4K91 ubiquitination?
Yes, knockout, point mutation, knock-in, and overexpression models can be generated.
What is the GO ID for histone H4K91 ubiquitin ligase activity?
GO:0141000.
What are the synonyms for GO:0141000?
Histone H4-K91 ubiquitin ligase activity; histone ubiquitin ligase activity (H4-K91 specific).
Why is H4K91 ubiquitination important for cancer therapy?
It affects chemosensitivity; targeting this pathway may overcome resistance.
Conclusion
GO:0141000, histone H4K91 ubiquitin ligase activity, represents a critical enzymatic function in chromatin biology and DNA repair. Its primary mediator, BBAP (DTX3L), catalyzes the ubiquitination of histone H4 at K91, a modification essential for recruiting repair factors and maintaining genomic stability. Dysregulation of this activity contributes to chemoresistance in diffuse large B-cell lymphoma, making it a promising target for therapeutic intervention. Continued research using advanced CRISPR models will further elucidate its mechanisms and disease relevance.
References
- 1. Johnson DP et al.. 2015. HDAC1,2 inhibition impairs EZH2- and BBAP-mediated DNA repair to overcome chemoresistance in EZH2 gain-of-function mutant diffuse large B-cell lymphoma.. Oncotarget 6(7):4863-87 PMID: 25605023
