Characterization of three XPG-defective patients identifies three missense mutations that impair repair and transcription.
Only 16 XPG-defective patients with 20 different mutations have been described. The current hypothesis is that missense mutations impair repair (xeroderma pigmentosum (XP) symptoms), whereas truncating mutations impair both repair and transcription (XP and Cockayne syndrome (CS) symptoms). We identified three cell lines of XPG-defective patients (XP40GO, XP72MA, and XP165MA). Patients' fibroblasts showed a reduced post-UVC cell survival. The reduced repair capability, assessed by host cell reactivation, could be complemented by XPG cDNA. XPG mRNA expression of XP165MA, XP72MA, and XP40GO was 83%, 97%, and 82.5%, respectively, compared with normal fibroblasts. XP165MA was homozygous for a p.G805R mutation; XP72MA and XP40GO were both compound heterozygous (p.W814S and p.E727X, and p.L778P and p.Q150X, respectively). Allele-specific complementation analysis of these five mutations revealed that p.L778P and p.W814S retained considerable residual repair activity. In line with the severe XP/CS phenotypes of XP72MA and XP165MA, even the missense mutations failed to interact with the transcription factor IIH subunits XPD and to some extent cdk7 in coimmunoprecipitation assays. Immunofluorescence techniques revealed that the mutations destabilized early recruitment of XP proteins to localized photodamage and delayed their redistribution in vivo. Thus, we identified three XPG missense mutations in the I-region of XPG that impaired repair and transcription and resulted in severe XP/CS.
Department of Dermatology, Venerology and Allergology, University Medical Center Göttingen, Göttingen, Germany.
Annika
A
Schäfer
Steffen
S
Schubert
Alexei
A
Gratchev
Christina
C
Seebode
Antje
A
Apel
Petra
P
Laspe
Lars
L
Hofmann
Andreas
A
Ohlenbusch
Toshio
T
Mori
Nobuhiko
N
Kobayashi
Anke
A
Schürer
Michael P
MP
Schön
Steffen
S
Emmert
D000595:Amino Acid Sequence; D002460:Cell Line; D003057:Cockayne Syndrome / Q000235:genetics* / Q000473:pathology; D004260:DNA Repair / Q000235:genetics* / Q000528:radiation effects; D004268:DNA-Binding Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D004720:Endonucleases / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects; D005838:Genotype; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D008969:Molecular Sequence Data; D020125:Mutation, Missense / Q000235:genetics*; D009687:Nuclear Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D014157:Transcription Factors / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics* / Q000528:radiation effects; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum / Q000235:genetics* / Q000473:pathology; D000099250:DNA Excision Repair Protein ERCC-5
D004268:DNA-Binding Proteins; D004720:Endonucleases; D009687:Nuclear Proteins; D014157:Transcription Factors; D000099250:DNA Excision Repair Protein ERCC-5