Oxidation of thymine by TET2 dioxygenase carrying leukemia-derived neomorphic mutations [WES-seq]

Deficiency of TET2 promotes the development of clonal hematopoiesis and various blood cancers, yet the mechanism by which TET2 mutations facilitate tumorigenesis remains to be explored. Here, we report that a subset of TET2 mutations identified in leukemia patients alter the substrate specificity of TET2 from acting on mC to thymine.

This neomorphic activity results from substitutions at key residues involved in the interactions with the mC base, including Asn1387 and His1904. Recombinant human TET2 proteins harboring the mutation of these residues can catalyze the oxidation of thymine to 5-hydroxymethyluracil (hmU) and 5-formyluracil (fU). Exogenous expression of the TET2 Asn1387Thr (N1387T) mutant in transfected cells leads to hmU accumulation, with the highest level in cells lacking SMUG1-initiated base excision repair pathway.