Functional interdependence of BRD4 and DOT1L in MLL leukemia
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Published on: January 7, 2019
Omer Gilan1,2, Enid Y N Lam1,2, Isabelle Becher3
1Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.
Abstract:
Targeted therapies against disruptor of telomeric silencing 1-like (DOT1L) and bromodomain-containing protein 4 (BRD4) are currently being evaluated in clinical trials. However, the mechanisms by which BRD4 and DOT1L regulate leukemogenic transcription programs remain unclear. Using quantitative proteomics, chemoproteomics and biochemical fractionation, we found that native BRD4 and DOT1L exist in separate protein complexes. Genetic disruption or small-molecule inhibition of BRD4 and DOT1L showed marked synergistic activity against MLL leukemia cell lines, primary human leukemia cells and mouse leukemia models. Mechanistically, we found a previously unrecognized functional collaboration between DOT1L and BRD4 that is especially important at highly transcribed genes in proximity to superenhancers. DOT1L, via dimethylated histone H3 K79, facilitates histone H4 acetylation, which in turn regulates the binding of BRD4 to chromatin. These data provide new insights into the regulation of transcription and specify a molecular framework for therapeutic intervention in this disease with poor prognosis.
Insights
Targeted therapies inhibiting disruptor of telomeric silencing 1-like (DOT1L) and bromodomain-containing protein 4 (BRD4) show synergistic activity in MLL leukemia. These proteins functionally collaborate at superenhancers, offering a new therapeutic framework.
Area of Science:
- Molecular biology
- Cancer research
- Epigenetics
Background:
- Disruptor of telomeric silencing 1-like (DOT1L) and bromodomain-containing protein 4 (BRD4) are targets in leukemia therapy.
- Mechanisms of BRD4 and DOT1L in regulating leukemogenic transcription are not fully understood.
Purpose of the Study:
- To elucidate the functional collaboration between DOT1L and BRD4 in MLL leukemia.
- To identify the molecular mechanisms underlying their regulation of leukemogenic transcription programs.
Main Methods:
- Quantitative proteomics
- Chemoproteomics
- Biochemical fractionation
- Genetic disruption and small-molecule inhibition studies in cell lines and mouse models.
Main Results:
- Native DOT1L and BRD4 exist in separate protein complexes.
- Combined inhibition of DOT1L and BRD4 demonstrates synergistic anti-leukemia activity.
- A novel functional collaboration between DOT1L and BRD4 was identified, particularly at superenhancers of highly transcribed genes.
- DOT1L-mediated histone H3 K79 methylation facilitates histone H4 acetylation, enhancing BRD4 chromatin binding.
Conclusions:
- DOT1L and BRD4 engage in a previously unrecognized functional collaboration crucial for MLL leukemia.
- This interaction, centered around superenhancers, provides a molecular framework for targeted therapeutic strategies against this aggressive cancer.
