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Protein complexes in nucleotide excision repair
1Imperial Cancer Research Fund, Clare Hall Laboratories, South Mimms, Hertfordshire, UK.
Abstract:
The main pathway by which mammalian cells remove DNA damage caused by UV light and some other mutagens is nucleotide excision repair (NER). The best characterised components of the human NER process are those proteins defective in the inherited disorder xeroderma pigmentosum (XP). The proteins known to be involved in the first steps of the NER reaction (damage recognition and incision-excision) are heterotrimeric RPA, XPA, the 6 to 9 subunit TFIIH, XPC-hHR23B, XPG, and ERCC1-XPF. Many interactions between these proteins have been found in recent years using different methods both in mammalian cells and for the homologous proteins in yeast. There are virtually no quantitative measurements of the relative strengths of these interactions. Higher order associations between these proteins in solution and even the existence of a complete "repairosome" complex have been reported, which would have implications both for the mechanism of repair and for the interplay between NER and other cellular processes. Nevertheless, evidence for a completely pre-assembled functional repairosome in solution is inconclusive and the order of action of repair factors on damaged DNA is uncertain.
Insights
Mammalian cells use nucleotide excision repair (NER) to remove DNA damage. Key NER proteins interact, but their precise assembly and order of action remain uncertain, impacting repair mechanisms.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Nucleotide excision repair (NER) is the primary pathway for removing DNA damage from UV light and mutagens in mammalian cells.
- Xeroderma pigmentosum (XP) is an inherited disorder linked to defects in key NER proteins.
- Proteins like RPA, XPA, TFIIH, XPC-hHR23B, XPG, and ERCC1-XPF are crucial for initial NER steps.
Purpose of the Study:
- To review the known protein interactions in the human nucleotide excision repair (NER) pathway.
- To highlight the lack of quantitative data on the strength of these protein interactions.
- To discuss the implications of potential higher-order protein complexes, such as a "repairosome," on NER mechanisms.
Main Methods:
- Literature review of studies investigating protein interactions in NER.
- Analysis of data from mammalian cells and yeast models.
- Assessment of evidence for pre-assembled repair complexes.
Main Results:
- Numerous interactions among NER proteins (RPA, XPA, TFIIH, XPC-hHR23B, XPG, ERCC1-XPF) have been identified.
- Quantitative data on the relative strengths of these interactions are largely absent.
- Evidence for a fully pre-assembled functional "repairosome" complex in solution is inconclusive.
Conclusions:
- The precise order of action and assembly of NER factors on damaged DNA is not definitively established.
- Understanding protein interactions is key to elucidating NER mechanisms and its interplay with other cellular processes.
- Further quantitative studies are needed to clarify the dynamic nature of NER complexes.