The 26S proteasome negatively regulates the level of overall genomic nucleotide excision repair
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Updated: Aug 14, 2026
Proofreading and DNA Repair Assay Using Single Nucleotide Extension and MALDI-TOF Mass Spectrometry Analysis
Published on: June 19, 2018
1Laboratory for Cancer Research, College of Pharmacy, Rutgers, The State University of New Jersey, 164 Frelinghuysen Road, Piscataway, NJ 08854-8020, USA.
Abstract:
Regulation of protein expression can be achieved through destruction of proteins by the 26S: proteasome. Cellular processes that are regulated by proteolysis include cell cycle progression, stress responses and differentiation. Several nucleotide excision repair proteins in yeast and humans, such as Rad23, Rad4 and XPB, have been shown to co-purify with Cim3 and Cim5, AAA ATPases of the 19S: proteasome regulatory subunit. However, it has not been determined if nucleotide excision repair is regulated through protein destruction. We measured nucleotide excision repair in yeast mutants that are defective in proteasome function and found that the repair of the transcribed and non-transcribed strands of an RNA polymerase II-transcribed reporter gene was increased in the absence of proteasome function. Additionally, overexpression of the Rad4 repair protein, which is bound to the repair/proteolytic factor Rad23, conferred higher rates of nucleotide excision repair. Based on our data we suggest that a protein (or proteins) involved in nucleotide excision repair or in regulation of repair is degraded by the 26S proteasome. We propose that decreased proteasome function enables increased DNA repair, due to the transient accumulation of a specific repair factor, perhaps Rad4.
Insights
The 26S proteasome regulates DNA repair by degrading key proteins. Impaired proteasome function enhances nucleotide excision repair, suggesting a role in maintaining genomic stability.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Protein degradation via the 26S proteasome regulates critical cellular processes.
- Nucleotide excision repair (NER) proteins have been linked to proteasome components, but a direct regulatory link was unconfirmed.
- The role of proteolysis in regulating DNA repair pathways remained largely unexplored.
Purpose of the Study:
- To investigate whether nucleotide excision repair (NER) is regulated by protein destruction mediated by the 26S proteasome.
- To determine the impact of proteasome dysfunction on DNA repair efficiency in yeast.
- To explore the potential role of specific NER proteins, like Rad4, in proteasome-mediated regulation.
Main Methods:
- Assessing nucleotide excision repair (NER) efficiency in yeast mutants with defects in proteasome function.
- Analyzing the repair of transcribed and non-transcribed strands of an RNA polymerase II-transcribed reporter gene.
- Evaluating the effect of overexpressing the Rad4 repair protein on NER rates.
Main Results:
- Nucleotide excision repair (NER) rates were significantly increased in yeast strains lacking functional proteasomes.
- Overexpression of the Rad4 repair protein led to elevated rates of nucleotide excision repair.
- These findings indicate that proteasome activity influences DNA repair capacity.
Conclusions:
- A protein (or proteins) integral to nucleotide excision repair (NER) or its regulation is likely degraded by the 26S proteasome.
- Reduced proteasome function appears to enhance DNA repair by allowing transient accumulation of repair factors, potentially including Rad4.
- This suggests a novel regulatory mechanism where proteasome-mediated protein degradation controls DNA repair efficiency and genomic stability.
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