Researchers at the Max Planck Institute of Immunobiology and Epigenetics (MPI-IE) in Freiburg report that a key assumption behind widely used BET-inhibitor drug strategies may be wrong: the BET proteins BRD2 and BRD4 are not interchangeable. The team says BRD2 helps prepare genes for activation while BRD4 acts later to enable productive transcription—differences that could contribute to the modest and unpredictable results seen with drugs that inhibit BET proteins broadly.
For more than a decade, scientists have tested a class of experimental cancer drugs known as BET inhibitors, designed to interfere with BET proteins that bind chromatin and help switch genes on. The approach has often worked in laboratory settings, but patient studies have generally produced modest benefits, along with side effects and limited ability to predict who will respond, according to a research summary released by MPI-IE.
In a study published in Nature Genetics on April 9, 2026, a team led by Asifa Akhtar reports evidence that two closely related BET proteins—BRD2 and BRD4—carry out different tasks at distinct steps of gene activation. BRD2, the researchers say, functions earlier by helping assemble and organize the molecular components needed to start transcription. BRD4 acts later, helping release RNA polymerase II so transcription can proceed.
Akhtar compared the process to a stage production, describing BRD2 as the “stage manager” that sets up the “props, costumes and actors,” before BRD4 helps initiate the “performance.”
The study also links BRD2’s behavior to histone acetylation marks placed on chromatin by the enzyme MOF. The researchers report that BRD2 is particularly sensitive to these marks: when MOF is removed, BRD2 can no longer remain attached to chromatin, while other BET proteins are described as being largely unaffected.
Beyond binding, the team reports that BRD2 forms clusters at gene sites that help concentrate transcription machinery where it is needed. First author Umut Erdogdu said the group tested the importance of clustering by removing only the portion of BRD2 responsible for forming clusters while leaving the rest of the protein intact; transcription slowed nearly as much as when the entire BRD2 protein was removed.
Taken together, the findings support a model in which broadly inhibiting BET proteins—including both BRD2 and BRD4—can disrupt multiple stages of gene activation and produce context-dependent effects. The researchers argue that future drug development may benefit from more selective strategies aimed at the distinct roles of BRD2 and BRD4, with the goal of improving effectiveness and predictability across different cancers.
