title: Reduced XPC DNA repair gene mRNA levels in clinically normal parents of xeroderma pigmentosum patients.
abstract: Xeroderma pigmentosum group C (XP-C) is a rare autosomal recessive disorder. Patients with two mutant alleles of the XPC DNA repair gene have sun sensitivity and a 1000-fold increase in skin cancers. Clinically normal parents of XP-C patients have one mutant allele and one normal allele. As a step toward evaluating cancer risk in these XPC heterozygotes we characterized cells from 16 XP families. We identified 15 causative mutations (5 frameshift, 6 nonsense and 4 splicing) in the XPC gene in cells from 16 XP probands. All had premature termination codons (PTC) and absence of normal XPC protein on western blotting. The cell lines from 26 parents were heterozygous for the same mutations. We employed a real-time quantitative reverse transcriptase-PCR assay as a rapid and sensitive method to measure XPC mRNA levels. The mean XPC mRNA levels in the cell lines from the XP-C probands were 24% (P<10(-7)) of that in 10 normal controls. This reduced XPC mRNA level in cells from XP-C patients was caused by the PTC that induces nonsense-mediated mRNA decay. The mean XPC mRNA levels in cell lines from the heterozygous XP-C carriers were intermediate (59%, P=10(-4)) between the values for the XP patients and the normal controls. This study demonstrates reduced XPC mRNA levels in XP-C patients and heterozygotes. Thus, XPC mRNA levels may be evaluated as a marker of cancer susceptibility in carriers of mutations in the XPC gene.
authors.affiliation: Basic Research Laboratory and Laboratory of Cellular Oncology, CCR, NCI, Bethesda, MD, USA.
authors.forename: Sikandar G
authors.initials: SG
authors.lastname: Khan
authors.forename: Kyu-Seon
authors.initials: KS
authors.lastname: Oh
authors.forename: Tala
authors.initials: T
authors.lastname: Shahlavi
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ueda
authors.forename: David B
authors.initials: DB
authors.lastname: Busch
authors.forename: Hiroki
authors.initials: H
authors.lastname: Inui
authors.forename: Steffen
authors.initials: S
authors.lastname: Emmert
authors.forename: Kyoko
authors.initials: K
authors.lastname: Imoto
authors.forename: Vanessa
authors.initials: V
authors.lastname: Muniz-Medina
authors.forename: Carl C
authors.initials: CC
authors.lastname: Baker
authors.forename: John J
authors.initials: JJ
authors.lastname: DiGiovanna
authors.forename: Deborah
authors.initials: D
authors.lastname: Schmidt
authors.forename: Arash
authors.initials: A
authors.lastname: Khadavi
authors.forename: Ahmet
authors.initials: A
authors.lastname: Metin
authors.forename: Engin
authors.initials: E
authors.lastname: Gozukara
authors.forename: Hanoch
authors.initials: H
authors.lastname: Slor
authors.forename: Alain
authors.initials: A
authors.lastname: Sarasin
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Kraemer
mesh_terms: D000293:Adolescent; D000328:Adult; D015153:Blotting, Western; D002648:Child; D018389:Codon, Nonsense / Q000235:genetics*; D017931:DNA Primers; D004260:DNA Repair / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D006579:Heterozygote; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009154:Mutation / Q000235:genetics*; D010290:Parents; D016133:Polymerase Chain Reaction; D022821:RNA Splice Sites; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D014983:Xeroderma Pigmentosum / Q000235:genetics* / Q000378:metabolism
chemical_list: D018389:Codon, Nonsense; D017931:DNA Primers; D004268:DNA-Binding Proteins; D022821:RNA Splice Sites; D012333:RNA, Messenger; C086984:XPC protein, human