Phosphorylation directly regulates the intrinsic DNA cytidine deaminase activity of activation-induced deaminase and APOBEC3G protein.

Zachary L Demorest, Ming Li, Reuben S Harris

The Journal of biological chemistry 2011 Jul 29

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The beneficial effects of DNA cytidine deamination by activation-induced deaminase (AID; antibody gene diversification) and APOBEC3G (retrovirus restriction) are tempered by probable contributions to carcinogenesis. Multiple regulatory mechanisms serve to minimize this detrimental outcome. Here, we show that phosphorylation of a conserved threonine attenuates the intrinsic activity of activation-induced deaminase (Thr-27) and APOBEC3G (Thr-218). Phospho-null alanine mutants maintain intrinsic DNA deaminase activity, whereas phospho-mimetic glutamate mutants are inactive. The phospho-mimetic variants fail to mediate isotype switching in activated mouse splenic B lymphocytes or suppress HIV-1 replication in human T cells. Our data combine to suggest a model in which this critical threonine acts as a phospho-switch that fine-tunes the adaptive and innate immune responses and helps protect mammalian genomic DNA from procarcinogenic lesions.

Citation

Zachary L Demorest, Ming Li, Reuben S Harris. Phosphorylation directly regulates the intrinsic DNA cytidine deaminase activity of activation-induced deaminase and APOBEC3G protein. The Journal of biological chemistry. 2011 Jul 29;286(30):26568-75