In B cells, antibody repertoire is created via two DNA instability complexes, one of which uses DNA cytosine deamination and is needed for immunoglobulin (Ig) diversification. Targeting of DNA deamination is poorly understood and mis-targeting can lead to genetic pathologies. Activation induced deaminase (AID) catalyses the hydrolytic deamination of cytosine residues, with the resulting uracil inducing DNA instability leading to Ig diversification. Recently AID has been implicated in inducing developmental DNA demethylation and pluripotent stem cell formation. Although transcription had been implicated in these mechanism, no direct evidence existed linking AID activity and transcription.The aim of this application is the analysis of AID containing transcription complexes and the role of RNA pol II modification during Ig diversification and epigenetics. Proteomic analysis of AID containing complexes from cytoplasm, nucleoplasm and chromatin revealed distinct associations, with the chromatin complex containing subunits of the elongating RNA pol II, transcription elongation and chromatin remodelling complexes. Biochemical analysis in vitro and in cell lines will identify direct interactions and domains and subsequent in vivo reconstitution of AID mutants determining in vivo relevance. Genetic analysis of candidates using transgene and knockout in cells and mice will delineate the molecular pathways of how transcription can alter the targeting or efficiency of AID. To further determine the role of the candidates on the loci, various forms of ChIP analysis will be utilised (e.g. double ChIP & ChIP-Seq); including the effect of RNA pol II modification, chromatin markers, and associated factors.Conclusions of this study will provide novel and detailed insight into the molecular mechanisms of AID regulation and how this will effect immune diversification and epigenetics, while providing new drug targets for AID pathologies (i.e. cancer and autoimmunity).