Relationship of the xeroderma pigmentosum group E DNA repair defect to the chromatin and DNA binding proteins UV-DDB and replication protein A.
Cells from complementation groups A through G of the heritable sun-sensitive disorder xeroderma pigmentosum (XP) show defects in nucleotide excision repair of damaged DNA. Proteins representing groups A, B, C, D, F, and G are subunits of the core recognition and incision machinery of repair. XP group E (XP-E) is the mildest form of the disorder, and cells generally show about 50% of the normal repair level. We investigated two protein factors previously implicated in the XP-E defect, UV-damaged DNA binding protein (UV-DDB) and replication protein A (RPA). Three newly identified XP-E cell lines (XP23PV, XP25PV, and a line formerly classified as an XP variant) were defective in UV-DDB binding activity but had levels of RPA in the normal range. The XP-E cell extracts did not display a significant nucleotide excision repair defect in vitro, with either UV-irradiated DNA or a uniquely placed cisplatin lesion used as a substrate. Purified UV-DDB protein did not stimulate repair of naked DNA by DDB- XP-E cell extracts, but microinjection of the protein into DDB- XP-E cells could partially correct the repair defect. RPA stimulated repair in normal, XP-E, or complemented extracts from other XP groups, and so the effect of RPA was not specific for XP-E cell extracts. These data strengthen the connection between XP-E and UV-DDB. Coupled with previous results, the findings suggest that UV-DDB has a role in the repair of DNA in chromatin.
Rapić Otrin
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V
Section on DNA Replication, Repair, and Mutagenesis, National Institute of Child Health and Human Development, Bethesda, Maryland 20892-2725, USA.
Kuraoka
I
I
Nardo
T
T
McLenigan
M
M
Eker
A P
AP
Stefanini
M
M
Levine
A S
AS
Wood
R D
RD
D002478:Cells, Cultured; D002843:Chromatin / Q000378:metabolism*; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000008:administration & dosage / Q000235:genetics* / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D008845:Microinjections; D051716:Replication Protein A; D012867:Skin / Q000378:metabolism / Q000528:radiation effects; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum / Q000235:genetics*
D002843:Chromatin; C091435:DDB1 protein, human; D004268:DNA-Binding Proteins; C497167:RPA1 protein, human; D051716:Replication Protein A