Figure 1.

Epigenomic modifications directing antibody-diversification processes somatic hypermutation (SHM) and CSR. Green core histones and associated modifications are involved in chromatin de-compaction and enable transcription through the immunoglobulin (Ig) locus. All factors above the locus are important for the generation of DSBs while everything below encourages mutagenic repair at the V region, and DSB repair at donor and acceptor S regions (Sμ and Sx, respectively). Blue histones and affiliated modifications help recruit or tether AID and other factors that facilitate production of DSBs. Purple DNA and RNA are linked with sequences and structures that facilitate AID recruitment or targeting. Red core histones and accessory modifications recruit DNA repair proteins to ensure excision of intervening C_H region for successful class switching as well as error-prone polymerases to the V region.