Abstract A174: Mechanistic elucidation of activation-induced deaminase (AID) in immunity and cancer

Abstract

Activation-induced cytidine deaminase (AID) plays a critical role in human immune system. It initiates both somatic hypermutation (SHM) and class switch recombination (CSR) of immunoglobulin (Ig) genes and possibly performs destructive mutations on non-Ig genes, related in cancer generation and development. Due to the aggregation behavior and extremely low activity of AID protein in vitro, the molecular basis of its function is still unclear. Using protein engineer approach, we successfully produced fully functional monomeric human AID mutants with dramatically elevated activity in vitro and intact CSR ability in vivo. Biochemistry data showed structured DNA with single strands joint feature, like G-quadruplex or partially branched DNA, can provide 10-20 fold AID affinity and 50-100 fold deaminase activity, suggests such structure can perform as direct AID recruiters in vivo. AID self-assembly upon DNA binding was observed and likely to be important for CSR. Stable AID-DNA complexes were purified in constant stoichiometry. Using crystallography method, we solved structures of AID alone and in complex with different DNA components in atomic resolution. Analyze on substrate binding interface and potential self-oligomerization interface together with abundant assay results support a structure based AID targeting and processing model during CSR and potential AID recruiting mechanism in causing off-target mutations. For the first time, our study reveals a closer look at this mystery protein, and provides solid basis for further investigation in AID function in antibody production and related diseases.

Citation Format: Qi Qiao, Li Wang, Feilong Meng, Hao Wu. Mechanistic elucidation of activation-induced deaminase (AID) in immunity and cancer. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A174.