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Updated: Jun 18, 2025

Author Spotlight: Quantitative Detection of DNA Protein Crosslinks and Their Post-Translational Modifications
Published on: April 21, 2023
Sequential post-translational modifications regulate damaged DNA-binding protein DDB2 function
Hidenori Kaneoka1, Kazuhiko Arakawa1, Yusuke Masuda1
1Department of Biomolecular Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan.
Abstract:
Nucleotide excision repair (NER) is a major DNA repair system and hereditary defects in this system cause critical genetic diseases (e.g. xeroderma pigmentosum, Cockayne syndrome and trichothiodystrophy). Various proteins are involved in the eukaryotic NER system and undergo several post-translational modifications. Damaged DNA-binding protein 2 (DDB2) is a DNA damage recognition factor in the NER pathway. We previously demonstrated that DDB2 was SUMOylated in response to UV irradiation; however, its physiological roles remain unclear. We herein analysed several mutants and showed that the N-terminal tail of DDB2 was the target for SUMOylation; however, this region did not contain a consensus SUMOylation sequence. We found a SUMO-interacting motif (SIM) in the N-terminal tail that facilitated SUMOylation. The ubiquitination of a SUMOylation-deficient DDB2 SIM mutant was decreased, and its retention of chromatin was prolonged. The SIM mutant showed impaired NER, possibly due to a decline in the timely handover of the lesion site to XP complementation group C. These results suggest that the SUMOylation of DDB2 facilitates NER through enhancements in ubiquitination.
Insights
SUMOylation of DNA damage-binding protein 2 (DDB2) aids nucleotide excision repair (NER) by enhancing ubiquitination. This process is crucial for DNA repair and preventing genetic diseases.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Nucleotide excision repair (NER) is a critical DNA repair pathway. Defects in NER cause severe genetic disorders like xeroderma pigmentosum.
- Damaged DNA-binding protein 2 (DDB2) is a key factor in DNA damage recognition within the NER pathway.
- Previous studies showed DDB2 undergoes SUMOylation after UV irradiation, but its function remained unclear.
Purpose of the Study:
- To investigate the physiological role of DDB2 SUMOylation in the NER pathway.
- To identify the specific region and mechanism of DDB2 SUMOylation.
Main Methods:
- Analysis of DDB2 mutants to pinpoint SUMOylation sites and functional motifs.
- Investigating the impact of SUMOylation deficiency on DDB2 ubiquitination and chromatin retention.
- Assessing the effect of DDB2 SUMOylation on the efficiency of the NER pathway.
Main Results:
- The N-terminal tail of DDB2 is SUMOylated, facilitated by a SUMO-interacting motif (SIM) despite lacking a consensus SUMOylation sequence.
- A DDB2 SIM mutant exhibited reduced ubiquitination and prolonged chromatin retention.
- This SIM mutant displayed impaired NER, suggesting a role in lesion site handover to downstream factors like XPC.
Conclusions:
- DDB2 SUMOylation is a crucial post-translational modification that enhances its ubiquitination.
- This SUMOylation process facilitates efficient nucleotide excision repair by promoting timely protein dynamics at DNA damage sites.
- Understanding DDB2 SUMOylation offers insights into NER pathway regulation and associated genetic diseases.
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