Structural modeling and analyses of genetic variations in the human XPC nucleotide excision repair protein

Abstract

Xeroderma pigmentosum C (XPC) is a key initiator in the global genome nucleotide excision repair pathway in mammalian cells. Inherited mutations in the XPC gene can cause xeroderma pigmentosum (XP) cancer predisposition syndrome that dramatically increases the susceptibility to sunlight-induced cancers. Various genetic variants and mutations of the protein have been reported in cancer databases and literature. The current lack of a high-resolution 3-D structure of human XPC makes it difficult to assess the structural impact of the mutations/genetic variations. Using the available high-resolution crystal structure of its yeast ortholog, Rad4, we built a homology model of human XPC protein and compared it with a model generated by AlphaFold. The two models are largely consistent with each other in the structured domains. We have also assessed the degree of conservation for each residue using 966 sequences of XPC orthologs. Our structure- and sequence conservation-based assessments largely agree with the variant’s impact on the protein’s structural stability, computed by FoldX and SDM. Known XP missense mutations such as Y585C, W690S, and C771Y are consistently predicted to destabilize the protein’s structure. Our analyses also reveal several highly conserved hydrophobic regions that are surface-exposed, which may indicate novel intermolecular interfaces that are yet to be characterized.

Communicated by Ramaswamy H. Sarma

Keywords:

• xeroderma pigmentosum
• XPC
• Rad4
• nucleotide excision repair
• X-ray crystallography
• homology model
• gene mutation
• polymorphism

Acknowledgments

We thank the members of the Min group.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was funded by National Science Foundation (NSF) (MCB- 2131806 to J.-H.M) and National Institute of Health (1R15GM147899 to J.-H.M).