EMBO J (2013) 32 10, 1381–1392. doi:; DOI: 10.1038/emboj.2013.42
A new study by Bevington and Boyes reports that expression of the IRF4 transcription factor is sufficient to prematurely activate assembly of immunoglobulin light chain loci in pro-B cells. Using this in vivo model, they provide evidence that transcription-coupled disruption of nucleosome cores may be a key event in unlocking DNA substrates for recognition and assembly by V(D)J recombinase.