The UvrABC Endonuclease (Excinuclease) Repair of DNA in Prokaryotes
What is Nucleotide Excision Repair (NER)?
As the name suggests it is a type of DNA repair mechanism. In nucleotide excision repair or NER, the damaged base along with a short stretch of healthy strand is removed and later the gap is refilled with correct nucleotides. Thus the NER pathway operates by ‘cut and patch’ mechanism. Even though nucleotide excision repair mechanism is present in prokaryotes and eukaryotes, the components of the pathways in both groups shows considerable variations. The prokaryotes shows relatively simple nucleotide excision repair mechanism, where as in eukaryotes, the NER pathway is quite complex with many enzymes.
Nucleotide Excision Repair can repair a variety of bulky lesions of the DNA such as pyrimidine dimers formed by UV irradiation and it can also remove chemically modified bases.
Classification of NER:
(1). UvrABC Endonuclease NER in Prokaryotes
(2). NER in Eukaryotes
There are two types of NER mechanism in eukaryotic cells
(a). Transcription Coupled Nucleotide Excision Repair (TC-NER)
(b). Global Genomic Nucleotide Excision Repair (GG-NER)
In this post, we will discuss only the NER mechanism of prokaryotes. The NER mechanism in prokaryotes is better known as UvrABC Endonuclease repair.
Enzymes involved in NER pathway of prokaryotes:
Nucleotide excision repair pathway in prokaryotes is orchestrated by UvrABC endonuclease complex. The NER method is also assisted by DNA polymerase I and DNA ligase enzymes. UvrABC endonuclease complex is a special class of endonuclease enzyme involved in DNA repair of prokaryotes. The name is derived from the root term ultraviolet radiation, since the level of most of these enzymes will be elevated in the bacterial cells when the cells are exposed to UV light.