TET2-mediated 5-hydroxymethylcytosine induces genetic instability and mutagenesis

Emna Mahfoudhi (1, 2, 3, 4) , Ibtissam A Talhaoui (2, 5) , Xenia Cabagnols (1, 2) , Véronique Della Valle (1, 2) , Lise Secardin (1, 2) , Philippe Rameau (2, 6) , Olivier A. Bernard (1, 2) , Alexander A. Ishchenko (2, 5) , Salem A Abbes (7, 3) , William Vainchenker (1, 2) , Murat A Saparbaev (2, 5) , Isabelle Plo (1, 2)

1 U1170 Inserm - Hématopoïèse normale et pathologique
2 IGR - Institut Gustave Roussy
3 UTM - Université de Tunis El Manar
4 LR11IPT07 - Laboratoire d'hématologie moléculaire et cellulaire
5 UMR 8200 - Stabilité Génétique et Oncogenèse
6 PFIC - Plateforme imagerie et cytométrie
7 Laboratoire d'Hématologie, Institut Pasteur de Tunis

The family of Ten-Eleven Translocation (TET) proteins is implicated in the process of active DNA demethy-lation and thus in epigenetic regulation. TET 1, 2 and 3 proteins are oxygenases that can hydroxylate 5-methylcytosine (5-mC) into 5-hydroxymethylcytosine (5-hmC) and further oxidize 5-hmC into 5-formylcytosine (5-fC) and 5-carboxylcytosine (5-caC). The base excision repair (BER) pathway removes the resulting 5-fC and 5-caC bases paired with a guanine and replaces them with regular cytosine. The question arises whether active modification of 5-mC residues and their subsequent elimination could affect the genomic DNA stability. Here, we generated two inducible cell lines (Ba/F3-EPOR, and UT7) over-expressing wild-type or catalytically inactive human TET2 proteins. Wild-type TET2 induction resulted in an increased level of 5-hmC and a cell cycle defect in S phase associated with higher level of phospho-rylated P53, chromosomal and centrosomal abnormalities. Furthermore, in a thymine-DNA glycosylase (Tdg) deficient context, the TET2-mediated increase of 5-hmC induces mutagenesis characterized by GC > AT transitions in CpG context suggesting a mutagenic potential of 5-hmC metabolites. Altogether, these data suggest that TET2 activity and the levels of 5-hmC and its derivatives should be tightly controlled to avoid genetic and chromosomal instabilities. Moreover, TET2-mediated active demethylation might be a very dangerous process if used to entirely demethylate the genome and might rather be used only at specific loci.

Mots clés: TDG; 5-hmC; Genetic instability; Cell cycle; TET2

Domaines: Génomique, Transcriptomique et Protéomique [q-bio.GN]

Emna Mahfoudhi, Ibtissam A Talhaoui, Xenia Cabagnols, Véronique Della Valle, Lise Secardin, et al.. TET2-mediated 5-hydroxymethylcytosine induces genetic instability and mutagenesis. DNA Repair, 2016, 43, pp.78 - 88. ⟨10.1016/j.dnarep.2016.05.031⟩. ⟨pasteur-01405648⟩