Nucleotide dual-incision

The mechanism of eukaryotic excinucleases is quite similar to that of the bacterial enzyme, although 16 polypeptides with no similarity to the E. coli excinuclease subunits are required for the dual incision. As described in Chapter 26, some of the nucleotide-excision repair and base-excision repair in eukaryotes is closely tied to transcription. Genetic deficiencies in nucleotide-excision repair in humans give rise to a variety of serious diseases (Box 25-1). 

The dual incisions results in the release of an oligonucleotide containing the damaged base that is on average about 27 nucleotides in length. The gap that is formed is filled in by either DNA polymerase 8 or DNA polymerase e in reactions dependent upon PCNA. DNA ligase I seals the final nick. 

Figure 6 Nucleotide excision repair in (A) E. coli and (B) humans. There are five basic steps of nucieotide excision repair (1) damage recognition, (2) dual incisions, (3) release of the excised oligomer, (4) repair synthesis to fill in the gap, and (5) ligation.

Evans E,Moggs JG, Hwang JR,EglyJM,Wood RD (1997) Mechanism of open complex and dual incision formation by human nucleotide excision repair factors. EMBO J 16 6559-73... 

Wakasugi, M., Reardon, J.T., and Sancar, A. (1997) The non-catalytic function of XPG protein during dual incision in human nucleotide excision repair./. Biol. Chem., 272,16030-16034. 

J. H., Gourdin, A.M., Wijgers, N., Dunand-Sauthier, I., Giglia-Mari, G., Clarkson, S.G., Vermeulen, W., and Scharer, O.D. (2009) Coordination of dual incision and repair synthesis in human nucleotide excision repair. EMBOJ., 28, 1111-1120. 

Figure 12.1 Outline of NER assay in human cell extracts. The hallmark of a successful mammalian NER dual-incision activity is the excision of internally 32P-labeled 24- to 32-nucleotide fragments containing the...

DNA duplex. Naegeli et al. have previously advanced a bipartite model of NER substrate discrimination that is initiated by the detection of disrupted Watson-Crick base-pairing followed by a lesion-sensing step that verifies the presence of a chemically altered nucleotide [29, 33]. The nature of the critically important verification step that leads to the dual incision is still not well understood [24]. The bipartite model is consistent with previous observatisons of Sugasawa et al. who found that XPC/HR23B binds to DNA that contains bubbles of several mismatched DNA bases in the absence of lesions or chemically modified nucleotides, but incisions occur only when a chemically modified base is also present [13, 35]. 

Y., Rodriguez, F., Kolbanovskii, A., Liu, Y., Zhang, L., Amin, S., Patel, D., Broyde, S., et al. (2009) The sequence dependence of human nucleotide excision repair efficiencies of benzoja] pyrene-derived DNA lesions insights into the structural factors that favor dual incisions. J. Mol. Biol., 386, 1193-1203. 

Fig. 1. Schematic illustration of nucleotide excision repair in prokaryotes and eukaryotes. The basic steps are conserved damage recognition and dual incisions to excise DNA damage, helicase activity to displace excised oligomer and repair factors, and resynthesis/ligation to restore the integrity of the DNA molecule. (See Color Insert.)...

Bessho, T., Mu, D., and Sancar, A. (1997). Initiation of DNA interstrand cross-link repair in humans The nucleotide excision repair system makes dual incisions 5 to the cross-linked base and removes a 22- to 28-nucleotide long damage free strand. 

Egly,J.-M. (2001). TFIIH From transcription to clinic. FEES Lett. 24884, 124-128. Evans, E., Moggs,J. G., Hwang, J. R., Egly,J.-M., and Wood, R. D. (1997). Mechanism of open complex and dual incision formation by human nucleotide excision repair factors. EMBOJ. 16, 6559-6573. 

The NER efficiencies in extracts from human HeLa cells of the (+)-trans-, (-)-trans-, and (+)-cis-anti-B[a]P-N2-dG adducts in the identical sequence context (5 -d(CCAT CG CTACC)) (5 -d(GGTAGCGATGG)) embedded in 135mer duplexes are shown in Figure 12.5(a). The lengths of the incision products coincide with those of the marker oligonucleotides around 26-32 nucleotides in length (lane M in Figure 12.5a), which is consistent with dual excision products obtained by the mamma-... 

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