hese proteins, defined as XPC (which is most always complexed with hHR23B), Transcription Factor II H (TFIIH), XPA, RPA, XPG, and ERCC1-XPF, travel along the surface of DNA in a constant search for these deformities. Upon recognition of the damage, specific endonuclease systems (XPG and ERCC-XPF) are put into action to cut out the altered nucleotide sequence. After removal of this sequence, DNA polymerases synthesize the proper sequence to fill the space, while DNA ligase finishes the job by connecting the newly synthesized sequence into the molecule (De Laat et all, 19!
             Experiments performed by Sofia J. Araujo and her colleagues provided experimental proof that the six above-named proteins were indeed the minimal set of factors required to initiate NER (Araujo et al 2000). Purified XPA, heterotrimeric RPA, and ERCC1-XPF produced by E. coli and purified XPG and XPC-hHR23B complex produced by insect cells was combined with TFIIH purified from HeLa cells. These six proteins were mixed and incubated with closed-circular plasmids possessing a
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