XPFNucleotide Excision Repair

Xerderma Pigmentosum (XP)

• UV Light Sensitivity• Early Age Freckling• Severe Sunburning• Keratosis• Neurological defects• Non-melonoma skin cancer ~10 yrs• basal and squamous cell carcinomas and

melanomas• 1000x increase in risk of cancer • autosomal recessive inheritance• tumor suppressor

Image from: institut national de recherche pédagogiquehttp://www.inrp.fr/Acces/biotic/gpe/dossiers/xeroderma/html/phenomacr.htm

XP: Complementation Groups• 8 subtypes identified by Cell-Fusion

Complementation Tests

• XPA-G : Nucleotide Excision Repair• XPV: DNA polymerase

Sugasawa 2008

UV Light and DNA Damage

• cyclobutane pyrimidinedimer (CPD) (A)

• pyrimidine -pyrimidone photoproduct (B)

• bulky base adducts

Sinha and Hӓder, 2002

Nucleotide Excision Repair

Sugasawa 2008

ERCC1-XPF Complex• XPF: 5’ endonuclease • ERCC1: interacts with DNA through helix–

hairpin–helix (HhH) motif at C-terminus• Only one recorded instance of human deficiency

• XPF Homologs:– S. cerevisiae: Rad1– Schizosaccharomyces pombe: rad16 – Drosophila melanogaster: MEI-9 – Mouse: ERCC4

Identification of cDNA of XPF

• Cloned using rt-PCR fragment of Rad1 in a humantestis cDNA library

• Encodes 115 kD protein

• Chromosome 16p13.1–13.2

Sijbers et al.1996

5’ Endonuclease Activity

Sijbers et al.1996

Chinese Hamster Cell Model

Shows ERCC1-XPF is necessary for 5’ incisions that only occur in coupled reactions

Mouse Models

Reduced Function ERCC1 mice

-growth retardation

-lack of subcutaneous fat

-no similar symptoms of XP

-liver and vascular defects

Weeda et al 1997

ERCC1 (-/-) Knockout Mice:

-died before weening

-liver failure

-kidney and vascular defects

McWhir et al 1993

XPF in Humans

• Majority of cases in Japan• Rare complementation group• Overall XP(all groups): 1 : 250,000 in US

(Cleaver et al 1999)

XP Treatments• Palliative Care• Avoidance of UV with frequent check ups• Keratosis treatment with isotrentinoin

(prevention) and ctyotherapy and fluorouracil

• Applied Genetics, Inc.'s – T4N5 endonuclease

study (Phase III)– T4 endonuclease V

encapsulated in liposome in cream

Future Directions

• XPF role in homologous recombination

• Its role outside of the NER complex

References Cleaver, J. L. Thompson, A Richardson, and J. States. 1999. A Summary

of Mutations in the UV-Sensitive Disorders: Xeroderma Pigmentosum, Cockayne Syndrome, and Trichothiodystrophy. Human Mutation. 14:9-22

de Laat W, AM. Sijbers, H. Odijk, Nicolaas GJ. Jaspers and J. Hoeijmakers. 1998. Mapping of interaction domains between human repairproteins ERCC1 and XPF 1. Nuc. Acid Res. 26:4146-52

Sijber, A. A. de Laat, R. Ariza, M. Biggerstaff, YF. Wei, J. Moggs, K. Carter, B. Shell, E. Evans, M. Jong, S. Rademakers, J. de Rooij, N. Jaspers, J. Hoeijmakers, and R. Wooods. 1996. Xeroderma Pigmentosum Group F Caused by a Defect in a Structure-Specific DNA Repair Endonuclease Cell 86:811-22

Sinha, R. and D. Häder. 2002. UV-induced DNA damage and repair: a review. Photochem. Photobiol. Sci. 1: 225-236

Sugasawa, K. 2008. Xeroderma pigmentosum genes: functions inside and outside DNA repair. Carcinogenesis 29: 455-465.

Weeda, G. I. Donker, J. de Wit, H. Morreau, R. Janssens, C.J. Vissers, A. Nigg, H. van Steeg, D. Bootsma and J.H.J. Hoeijmakers.1997. Disruption of mouse ERCC1 results in a novel repair syndrome with growth failure, nuclear abnormalities and senescence.Current Biology, 7:427–439

Xeroderma Pigmentosum. Updated 3/16/2008. http://en.wikipedia.org/wiki/Xeroderma_pigmentosum

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