Extensive gene conversion at the PMS2 DNA mismatch repair locus.
Mutations of the PMS2 DNA repair gene predispose to a characteristic range of malignancies, with either childhood onset (when both alleles are mutated) or a partially penetrant adult onset (if heterozygous). These mutations have been difficult to detect, due to interference from a family of pseudogenes located on chromosome 7. One of these, the PMS2CL pseudogene, lies within a 100-kb inverted duplication (inv dup), 700 kb centromeric to PMS2 itself on 7p22. Here, we show that the reference genomic sequences cannot be relied upon to distinguish PMS2 from PMS2CL, because of sequence transfer between the two loci. The 7p22 inv dup occurred prior to the divergence of modern ape species (15 million years ago [Mya]), but has undergone extensive sequence homogenization. This process appears to be ongoing, since there is considerable allelic diversity within the duplicated region, much of it derived from sequence exchange between PMS2 and PMS2CL. This sequence diversity can result in both false-positive and false-negative mutation analysis at this locus. Great caution is still needed in the design and interpretation of PMS2 mutation screens.
Hayward
Bruce E
BE
Leeds Institute of Molecular Medicine, University of Leeds and Yorkshire Regional Genetics Service, St James's University Hospital, Leeds, United Kingdom.
De Vos
Michel
M
Valleley
Elizabeth M A
EM
Charlton
Ruth S
RS
Taylor
Graham R
GR
Sheridan
Eamonn
E
Bonthron
David T
DT
D000251:Adenosine Triphosphatases / Q000235:genetics*; D000483:Alleles; D000818:Animals; D020137:Base Pair Mismatch; D001483:Base Sequence; D005075:Biological Evolution; D002897:Chromosomes, Human, Pair 7; D017931:DNA Primers; D004260:DNA Repair / Q000235:genetics*; D045643:DNA Repair Enzymes / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics*; D005091:Exons; D005785:Gene Conversion; D006801:Humans; D000070976:Mismatch Repair Endonuclease PMS2; D009154:Mutation; D016133:Polymerase Chain Reaction; D011323:Primates; D011544:Pseudogenes
D017931:DNA Primers; D004268:DNA-Binding Proteins; D000251:Adenosine Triphosphatases; C094934:PMS2 protein, human; D000070976:Mismatch Repair Endonuclease PMS2; D045643:DNA Repair Enzymes