Molecular analysis of mutations in DNA polymerase eta in xeroderma pigmentosum-variant patients.
Xeroderma pigmentosum variant (XP-V) cells are deficient in their ability to synthesize intact daughter DNA strands after UV irradiation. This deficiency results from mutations in the gene encoding DNA polymerase eta, which is required for effecting translesion synthesis (TLS) past UV photoproducts. We have developed a simple cellular procedure to identify XP-V cell strains, and have subsequently analyzed the mutations in 21 patients with XP-V. The 16 mutations that we have identified fall into three categories. Many of them result in severe truncations of the protein and are effectively null alleles. However, we have also identified five missense mutations located in the conserved catalytic domain of the protein. Extracts of cells falling into these two categories are defective in the ability to carry out TLS past sites of DNA damage. Three mutations cause truncations at the C terminus such that the catalytic domains are intact, and extracts from these cells are able to carry out TLS. From our previous work, however, we anticipate that protein in these cells will not be localized in the nucleus nor will it be relocalized into replication foci during DNA replication. The spectrum of both missense and truncating mutations is markedly skewed toward the N-terminal half of the protein. Two of the missense mutations are predicted to affect the interaction with DNA, the others are likely to disrupt the three-dimensional structure of the protein. There is a wide variability in clinical features among patients, which is not obviously related to the site or type of mutation.
Broughton
Bernard C
BC
Genome Damage and Stability Centre, University of Sussex, Falmer, Brighton BN1 9RR, United Kingdom.
Cordonnier
Agnes
A
Kleijer
Wim J
WJ
Jaspers
Nicolaas G J
NG
Fawcett
Heather
H
Raams
Anja
A
Garritsen
Victor H
VH
Stary
Anne
A
Avril
Marie-Françoise
MF
Boudsocq
Francois
F
Masutani
Chikahide
C
Hanaoka
Fumio
F
Fuchs
Robert P
RP
Sarasin
Alain
A
Lehmann
Alan R
AR
D002460:Cell Line; D004252:DNA Mutational Analysis; D004260:DNA Repair / Q000235:genetics; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry / Q000235:genetics*; D016368:Frameshift Mutation; D014644:Genetic Variation; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D020125:Mutation, Missense; D010641:Phenotype; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion; D014983:Xeroderma Pigmentosum / Q000201:enzymology* / Q000235:genetics*; D000099270:Y-Family DNA Polymerases
D004259:DNA-Directed DNA Polymerase; C112338:Rad30 protein; D000099270:Y-Family DNA Polymerases