The DNA repair gene MBD4 ( MED1 ) is mutated in human carcinomas with microsatellite instability

• Published in: Nature genetics Vol. 23; no. 3; pp. 266 - 268
• Main Authors: Bellacosa, Alfonso, Riccio, Antonio, Aaltonen, Lauri A, Godwin, Andrew K, Loukola, Anu, Percesepe, Antonio, Salovaara, Reijo, Masciullo, Valeria, Genuardi, Maurizio, Paravatou-Petsotas, Maria, Bassi, Daniel E, Ruggeri, Bruce A, Klein-Szanto, Andres J.P, Testa, Joseph R, Neri, Giovanni
• Format: Journal Article
• Language: English
• Published: United States 01.11.1999
• Subjects: colorectal carcinoma; DNA Mutational Analysis; DNA Repair - genetics; Endodeoxyribonucleases - genetics; Endodeoxyribonucleases - physiology; Gene Frequency; Humans; Loss of Heterozygosity; MBD4 gene; MED1 gene; methyl-CpG-binding endonuclease 1; Microsatellite Repeats - genetics; mismatch repair; Mutation; Neoplasms - enzymology; Neoplasms - genetics; Neoplasms - pathology; Polymorphism, Single-Stranded Conformational; Trinucleotide Repeat Expansion - genetics
• ISSN: 1061-4036; 1546-1718
• DOI: 10.1038/15443

Most tumours arising in individuals affected with hereditary non-polyposis colorectal cancer (HNPCC) are characterized by microsatellite instability (MSI). MSI is also detected in a subset of sporadic colorectal and extra-colonic carcinomas. MSI is the consequence of non-repaired, slippage-induced strand misalignments that occur during DNA replication, and is the hall-mark of a defective DNA mismatch repair (MMR) system. We recently identified a new human DNA repair gene, MBD4 (also known as MED1, for methyl-CpG binding endonuclease 1), that encodes an MLH1 interactor. This protein binds to fully and hemimethylated DNA, is homologous to bacterial DNA repair glycosylases/lyases and has endonuclease activity. Transfection of an MMR-proficient cell line with a dominant-negative deletion construct resulted in an MSI phenotype, suggesting that this mutant perturbs endogenous DNA repair. On the basis of these findings, we proposed that MBD4 is a DNA repair gene that may be involved in MMR and may regulate genomic stability. This prompted us to investigate its role in human tumours displaying MSI. The MBD4 coding sequence harbours four potential hypermutable tracks: one (A) sub(10) track at codons 310-313, and three (A) sub(6) sequences at codons 247-248, 280-282 and 327-329. We screened a panel of both MSI and microsatellite-stable (MSS) primary tumours and cell lines for mutations in these polyadenine tracks by PCR, followed by single-strand conformational polymorphism (SSCP) analysis and direct sequencing. In addition, we cloned PCR products and obtained the sequence of multiple clones, thus allowing determination of the mutations.