Analysis of the human APC mutation spectrum in a saccharomyces cerevisiae strain with a mismatch repair defect.
Somatic APC mutations in colorectal tumors with an RER phenotype reflect excessive frameshift mutations, especially in simple repetition tracts within the coding sequence. Because this type of mutation is characteristic of cells with a deficient DNA MMR system, the APC mutation signature of RER tumors may be attributable to a defect in the MMR system. However, there is little experimental evidence to prove that the spectrum of mutations and the APC gene distribution are directly influenced by MMR system defects. We therefore examined the mutation spectrum of the MCR of the APC gene after transfection into both MMR-proficient and MMR-deficient yeast strains and compared it with a previously reported human APC mutation database. Small insertions or deletions in mono- or dinucleotide repeats were more common in the MMR-deficient than in the MMR-proficient strain (91.2% vs. 38.1%, Fisher's exact test p < 0.0001). Furthermore, the 2 mutation hot spots, 4385-4394(AG)(5) and 4661-4666(A)(6), found in the yeast system corresponded with those in human tumors. Combining our data with those from human tumors, there appears to be hypermutable mutations in specific simple repetitive sequences within the MCR, which are more prevalent in MMR-deficient cells and RER tumors than in MMR-proficient cells and non-RER tumors. We therefore consider that the differences in the spectra of RER and non-RER tumors are attributable at least in part to the MMR system of the host cells.
Otsuka
Kazunori
K
Department of Clinical Oncology, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan.
Suzuki
Takao
T
Shibata
Hiroyuki
H
Kato
Satoshi
S
Sakayori
Masato
M
Shimodaira
Hideki
H
Kanamaru
Ryunosuke
R
Ishioka
Chikashi
C
D025601:Adenomatous Polyposis Coli Protein / Q000235:genetics*; D020137:Base Pair Mismatch / Q000235:genetics*; D015179:Colorectal Neoplasms / Q000209:etiology* / Q000235:genetics; D004252:DNA Mutational Analysis; D017931:DNA Primers / Q000737:chemistry; D004260:DNA Repair / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000172:deficiency*; D018900:Dinucleotide Repeats / Q000235:genetics; D005656:Fungal Proteins; D017491:Genes, APC; D006801:Humans; D051718:MutS Homolog 2 Protein; D009154:Mutation / Q000235:genetics*; D010957:Plasmids; D016133:Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins
D025601:Adenomatous Polyposis Coli Protein; D017931:DNA Primers; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; C489751:MSH2 protein, S cerevisiae; D051718:MutS Homolog 2 Protein