Thymine DNA glycosylase is a CRL4Cdt2 substrate

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• CRL4(Cdt2) is an E3 ubiquitin ligase that degrades proteins during S phase and DNA damage.
• Degradation is mediated by coupling ubiquitylation to DNA-bound PCNA via a PIP degron motif.
• Known substrates include Cdt1, Set8, and p21, crucial for cell cycle regulation.

Purpose of the Study:

• To investigate whether CRL4(Cdt2) targets thymine DNA glycosylase (TDG) for degradation.
• To elucidate the mechanism and developmental regulation of TDG degradation.

Main Methods:

• Utilized Xenopus egg extract system to study protein ubiquitylation and degradation.
• Analyzed TDG's sequence for a PCNA-interacting peptide (PIP) degron motif.
• Examined TDG expression during Xenopus development.

Main Results:

• TDG contains a conserved PIP degron motif, suggesting it is a substrate for CRL4(Cdt2).
• TDG is ubiquitylated and degraded in a PCNA-, Cdt2-, and PIP degron-dependent manner during DNA repair and replication in Xenopus egg extract.
• TDG expression is downregulated by CRL4(Cdt2) during Xenopus gastrulation.

Conclusions:

• CRL4(Cdt2) targets the DNA repair enzyme TDG for degradation.
• This expands the known substrate repertoire of CRL4(Cdt2) to include a key enzyme in base excision repair and DNA demethylation.
• CRL4(Cdt2)-mediated TDG degradation is important for regulating its levels during development.