Glycine-N-methyltransferase (GNMT) is a protein with multiple functions. It can affect genetic stability by (1) regulating the ratio of S-adenosylmethionine to S-adenosylhomocystine and (2) binding to folate. In addition to act as a tumor suppressor for liver cancer, GNMT participated in the detoxification pathway by interacting with environmental carcinogens [such as benzo(a)pyrene (BaP), aflatoxin B1 (AFB1)] and decreasing subsequent DNA adducts formation and cytotoxicity. GNMT was primarily expressed in cytoplasm and partially translocated to cell nuclei after BaP treatment. Despite the mechanism of GNMT nuclear translocation remains unclear, it has been shown that the phosphorylation modification is important for GNMT nuclear translocation. The results from LC-MS/MS (liquid chromatography-tandem mass spectrometry) analysis showed that serine 9 of GNMT was phosphorylated after BaP treatment. The GNMTS9A mutant did not undergo nuclear translocation after BaP treatment by using indirect immunofluorescence assay. GNMT serine 9 was identified within an Akt1 consensus site by Scansite program. The co-immunoprecipitaion assay demonstrated that GNMT interacts with Akt. Akt phosphorylated GNMT only on serine 9 in vitro. Furthermore, BaP induced GNMT nuclear translocation was blocked by LY294002 treatment. In conclusion, the results suggested that the Serine 9, can be phosphorylated by Akt1, is an important phosphorylation site responsible for GNMT nuclear translocation after BaP treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1335. doi:10.1158/1538-7445.AM2011-1335