Lysine acetylation is an important epigenetic mark regulating gene transcription and chromatin
structure. Acetylated lysine residues are specifically recognized by bromodomains,
small protein interaction modules that read these modification in a sequence and acetylation
dependent way regulating the recruitment of transcriptional regulators and chromatin
remodelling enzymes to acetylated sites in chromatin. Recent studies revealed that bromodomains
are highly druggable protein interaction domains resulting in the development of a
large number of bromodomain inhibitors. BET bromodomain inhibitors received a lot of
attention in the oncology field resulting in the rapid translation of early BET bromodomain
inhibitors into clinical studies. Here we investigated the effects of mutations present as polymorphism
or found in cancer on BET bromodomain function and stability and the influence
of these mutants on inhibitor binding. We found that most BET missense mutations localize
to peripheral residues in the two terminal helices. Crystal structures showed that the three
dimensional structure is not compromised by these mutations but mutations located in
close proximity to the acetyl-lysine binding site modulate acetyl-lysine and inhibitor binding.
Most mutations affect significantly protein stability and tertiary structure in solution, suggesting
new interactions and an alternative network of protein-protein interconnection as a consequence
of single amino acid substitution. To our knowledge this is the first report studying
the effect of mutations on bromodomain function and inhibitor binding
