Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we'll assume that you are happy to receive all cookies and you won't see this message again. Click 'Find out more' for information on how to change your cookie settings.

Defects in the xeroderma pigmentosum type B (XPB) gene (ERCC3), a DNA helicase involved in nucleotide excision repair (NER) and an essential subunit of the basal transcription factor, TFIIH, have been described in only three families. We report three new XPB families: one has two sisters with relatively mild xeroderma pigmentosum (XP) symptoms not previously associated with XPB mutations and two have severe XP/Cockayne syndrome (CS) complex symptoms. All XP-B cells had reduced NER and post-ultraviolet (UV) cell viability. Surprisingly, cells from the milder XP sisters had the same missense mutation (c.296T>C, p.F99S) that was previously reported in two mild XP/CS complex brothers. These cells had higher levels of XPB protein than the severely affected XP/CS complex patients. An XPB expression vector with the p.F99S mutation partially complemented the NER defect in XP-B cells. The three severely affected XP/CS complex families all have the same splice acceptor site mutation (c.2218-6C>A, p.Q739insX42) in one allele. This resulted in alteration of 41 amino acids at the C terminus, producing partial NER complementation. This limited number of mutations probably reflects the very restricted range of alterations of this vital protein that are compatible with life. We found new mutations in the second allele yielding markedly truncated proteins in all five XP or XP/CS complex families: c.1273C>T, p.R425X; c.471+1G>A, p.K157insTSDSX; c.807-808delTT, p.F270X; c.1421-1422insA, p.D474EfsX475; and c.1633C>T, p.Q545X. The remarkable phenotypic heterogeneity of XPB is associated with partially active missense mutations in milder patients while severe XP/CS complex patients have nonsense mutations in both alleles with low levels of altered XPB proteins.

Original publication

DOI

10.1002/humu.20392

Type

Journal article

Journal

Human mutation

Publication Date

11/2006

Volume

27

Pages

1092 - 1103

Addresses

DNA Repair Section, Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892-4258, USA.

Keywords

Humans, Melanoma, Carcinoma, Basal Cell, Eye Neoplasms, Xeroderma Pigmentosum, Cockayne Syndrome, Demyelinating Diseases, Abnormalities, Multiple, Photosensitivity Disorders, DNA Helicases, DNA-Binding Proteins, RNA, Nuclear Family, Ultraviolet Rays, Cell Survival, DNA Repair, Gene Expression, Alternative Splicing, Heterozygote, Phenotype, Mutation, Polymorphism, Genetic, Genome, Human, Adult, Middle Aged, Female, Male