Neomorphic leukemia-derived mutations in the TET2 enzyme induce genome instability via a substrate shift from 5-methylcytosine to thymine

• DOI: 10.1073/pnas.2418318122
• Publication Date: 2025-01-28T18:40:11Z
• Authors: Guang-Bo Jin; Shao-Qin Rong; Dong-Rui Yin; Zhou-Hao Deng; Xiao Ding; Meng-Yao Sheng; Hai Gao; Rahul M. Kohli; Guo-Liang Xu; Dan Zhou
• Keywords: 5-Methylcytosine; Thymine; HEK 293 cells

Ten-eleven translocation (TET) enzymes oxidize 5-methylcytosine (mC) in DNA, contributing to the regulation of gene transcription. Diverse mutations TET2 are frequently found various blood cancers, yet full scope their functional consequences has been unexplored. Here, we report that a subset identified leukemia patients alter substrate specificity from acting on mC thymine. This neomorphic activity results substitutions at key residues involved interactions with base, including Asn1387 and His1904. Recombinant human proteins harboring mutation these can catalyze oxidation thymine 5-hydroxymethyluracil (hmU) 5-formyluracil (fU). Exogenous expression mutant Asn1387Thr (N1387T) HEK293T cells leads hmU accumulation, levels further increased lacking glycosylase SMUG1. Endogenous knock-in N1300T, murine equivalent N1387T, mouse embryonic stem induces production, causing DNA lesions transcriptional activation damage response genes. N1300T accumulate more additional extended culture exhibit heightened sensitivity ATR inhibition compared Tet2 knockout cells. Our study reveals certain patient-derived acquire unexpected gain-of-function activities beyond impairing oxidation, offering fresh perspective diverse molecular etiology TET2-related leukemogenesis.