TET2-mediated 5-hydroxymethylcytosine induces genetic instability and mutagenesis

Area of Science:

• Epigenetics and Molecular Biology
• Genomic Stability and DNA Repair

Background:

• Ten-Eleven Translocation (TET) proteins are key regulators of active DNA demethylation.
• TET proteins catalyze the oxidation of 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC) and further derivatives.
• The base excision repair (BER) pathway processes these oxidized bases, raising questions about genomic DNA stability.

Purpose of the Study:

• To investigate the impact of TET2 activity on genomic DNA stability.
• To determine if TET2-mediated 5-hmC accumulation induces mutagenesis.
• To assess the consequences of TET2 overexpression on cell cycle and chromosomal integrity.

Main Methods:

• Generation of inducible cell lines (Ba/F3-EPOR, UT7) overexpressing wild-type or inactive TET2.
• Analysis of 5-hmC levels, cell cycle progression, and DNA damage markers (phosphorylated P53).
• Assessment of chromosomal and centrosomal abnormalities, and mutagenesis in thymine-DNA glycosylase (Tdg)-deficient cells.

Main Results:

• Wild-type TET2 induction elevated 5-hmC levels and caused S-phase cell cycle defects.
• Overexpression of TET2 led to increased phosphorylated P53, chromosomal, and centrosomal abnormalities.
• In Tdg-deficient cells, TET2-induced 5-hmC promoted GC>AT transitions, indicating mutagenic potential.

Conclusions:

• TET2 activity and 5-hmC levels must be tightly regulated to prevent genetic and chromosomal instability.
• The accumulation of 5-hmC and its derivatives can lead to mutagenesis.
• Extensive genome-wide demethylation via TET2 may pose risks and should be locus-specific.