Epigenetic targeting of activation-induced cytidine deaminase

Precisely how AID is recruited to these off-target sites is not entirely understood. To gain further insight into how AID selects its targets we compared AID-mediated translocations in two different cell types, B cells and mouse embryonic fibroblasts (MEFs). AID targets a distinct set of hotspots in the two cell types. In both cases, hotspots are concentrated in highly transcribed but stalled genes. However, transcription alone is insufficient to recruit AID activity. Comparison of genes similarly transcribed in B cells and MEFs but targeted in only one of the two cell types reveals a common set of epigenetic features associated with AID recruitment in both cell types. AID target genes are enriched in chromatin modifications associated with active enhancers (such as H3K27Ac) and marks of active transcription (such as H3K36me3) in both fibroblasts and B cells, indicating that these features are universal mediators of AID recruitmen Analysis of total mRNA and PolII loading in activated B lymphocytes and Mouse Embryonic Fibroblasts (MEFs)