Development of Murine Leukemia Virus Integrase-Derived Peptides That Bind Brd4 Extra-Terminal Domain as Candidates for Suppression of Acute Myeloid Leukemia
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Updated: Oct 16, 2025
Amplification, Next-generation Sequencing, and Genomic DNA Mapping of Retroviral Integration Sites
Published on: March 22, 2016
Enming Xing1, Nandini Surendranathan2, Xiaotian Kong3
1Division of Medicinal Chemistry and Pharmacognosy, The Ohio State University, Columbus, Ohio 43210, United States.
Abstract:
The bromodomain and extra-terminal (BET) domain family of proteins, which include its prototypical member Brd4, is implicated in a variety of cancers and viral infections due to their interaction with cellular and viral proteins. BET proteins contain two bromodomains, a common protein motif that selectively binds acetylated lysine on histones. However, they are structurally distinct from other bromodomain-containing proteins because they encode a unique C-terminal extra-terminal (ET) domain that is important for the protein-protein interactions including jumonji C-domain-containing protein 6 (JMJD6) and histone-lysine N-methyltransferase NSD3 (NSD3). Brd4 functions primarily during transcription as a passive scaffold linking cellular and viral proteins to chromatin. The rapid development of clinical inhibitors targeting Brd4 highlights the importance of this protein as an anticancer target. Current therapeutic approaches focus on the development of small molecule acetylated lysine mimics of histone marks that block the ability of the bromodomains to bind their chromatin marks. Thus far, bromodomain-targeted agents have shown dose-limiting toxicities due to off-target effects on other bromodomain-containing proteins. Here, we exploited a viral-host protein interaction interface to design peptides for the disruption of BET protein function. A murine leukemia virus (MLV) integrase-derived peptide (ET binding motif, EBM) and its shorter minimal binding motif (pentapeptide LKIRL) were sufficient to directly bind the Brd4 ET domain and reduce cellular proliferation of an acute myeloid leukemia cell line. Using computational and biochemical approaches, we identified the minimal essential contacts between EBM and LKIRL peptides and the Brd4 ET domain. Our findings provide a structural foundation for inhibiting BET/Brd4-mediated cancers by targeting the ET domain with small peptide-based inhibitors.
Insights
Researchers designed peptide inhibitors targeting the Brd4 ET domain to disrupt bromodomain and extra-terminal (BET) protein function in cancer. This approach offers a new strategy for developing targeted cancer therapies with potentially fewer side effects than current methods.
Area of Science:
- Molecular Biology
- Cancer Research
- Drug Discovery
Background:
- Bromodomain and extra-terminal (BET) proteins, including Brd4, are crucial in cancer and viral infections by interacting with cellular and viral proteins.
- Brd4 acts as a scaffold in transcription, linking proteins to chromatin, making it a key anticancer target.
- Current inhibitors mimic histone marks to block BET bromodomains, but cause toxicities due to off-target effects.
Purpose of the Study:
- To design peptide inhibitors that disrupt BET protein function by targeting the Brd4 ET domain.
- To identify the minimal binding motif and structural interactions for peptide-based inhibition of Brd4.
Main Methods:
- Exploited a viral-host protein interaction interface to design peptides.
- Utilized computational and biochemical approaches to analyze peptide-Brd4 ET domain interactions.
- Assessed the effect of peptides on acute myeloid leukemia cell proliferation.
Main Results:
- A murine leukemia virus (MLV) integrase-derived peptide (EBM) and a pentapeptide (LKIRL) directly bound the Brd4 ET domain.
- These peptides reduced the cellular proliferation of an acute myeloid leukemia cell line.
- Identified the minimal essential contacts between the peptides and the Brd4 ET domain.
Conclusions:
- Peptide-based inhibitors targeting the Brd4 ET domain can disrupt BET protein function.
- This strategy provides a structural basis for developing novel peptide-based inhibitors for BET/Brd4-mediated cancers.
- Targeting the ET domain offers a potential alternative to current bromodomain-focused therapies, possibly reducing off-target toxicities.
