How does nucleotide excision repair work?
Nucleotide excision repair is a precise, stepwise process that removes bulky DNA lesions, such as those caused by UV light. In E. coli, it begins with UvrA and UvrB scanning the DNA for distortions. UvrA then leaves, and UvrC binds to make two cuts—one on each side of the damage. The damaged oligonucleotide is removed by UvrD helicase, and DNA polymerase I fills the gap using the undamaged strand as a template. Finally, DNA ligase seals the nick. In humans, the process is more complex, involving over 20 proteins like XPA for damage verification and XPG for incision. I often compare this to a tailor mending a torn garment: the tailor cuts out the frayed fabric, patches it with new thread, and sews it back together. Hard work and perseverance can overcome any obstacle, and this pathway exemplifies nature's elegance in preserving genetic integrity.
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