Purpose: To determine damaged DNA-binding protein 2-gene expression levels in vitro and ex vivo, and the degree of DNA repair in damaged DNA-binding protein 2-overexpressing cultured human corneal endothelium after ultraviolet irradiation.
Methods: Constitutive damaged DNA-binding protein 2-gene expression levels in various human tissues were determined by semi-quantitative reverse transcription-polymerase chain reactions. The dynamics of nucleotide excision repair-related gene expression in cultured human corneal endothelium were investigated in a ribonuclease protection assay after ultraviolet-irradiation. The effect of damaged DNA-binding protein 2 on DNA repair was studied after ultraviolet-irradiation in cultured human corneal endothelium infected with adenovirus carrying damaged DNA-binding protein 2.
Results: Human corneal endothelium and epithelium in the donor cornea had the highest constitutive damaged DNA-binding protein 2-gene expression of the various human tissues studied. Gene expression level dynamics associated with nucleotide excision repair factors after ultraviolet-irradiation showed that the increase in the rate of damaged DNA-binding protein 2-gene expression in cultured human corneal endothelium was highest of the nucleotide excision repair-related genes studied. An in vivo DNA repair assay showed that DNA repair efficiency in damaged DNA-binding protein 2-overexpressing cultured human corneal endothelium after ultraviolet-irradiation was significantly improved as compared with that in the control human corneal endothelium.
Conclusion: The human corneal endothelium abundantly expresses the damaged DNA-binding protein 2-gene that is produced efficiently on ultraviolet exposure. This overexpressed damaged DNA-binding protein 2 in the human corneal endothelium contributes to the protection system against DNA damage after ultraviolet-irradiation. Our findings show a critical role for damaged DNA-binding protein 2 in DNA repair to maintain the human corneal endothelium function.