During FY14 we accomplished the following: 1. We carried out in vitro studies of 12/23 RSS-dependent coupled cleavage reactions of RAG1/2 on chromatin assembled templates using nucleosomes assembled from fully recombinant histones with specific post-translational modifications. These studies were carried out in collaboration with Dr. Stephen Desiderio (Johns Hopkins School of Medicine). 2. We carried out additional in vitro transcription experiments to study promoter utilization and polymerase pausing on different VH gene promoters. However, because of experimental problems we have currently put these experiments on hold. These studies were carried out in collaboration with Dr. Patricia Gearhart (LMBI, NIA)