RESUMO
Although most of the pertinent data on the sequence-directed processes leading to genome rearrangements (GRs) have come from studies on somatic tissues, little is known about GRs in the germ line of patients with hereditary disorders. This study aims at identifying DNA motifs and higher order structures of genome architecture, which can result in losses and gains of genetic material in the germ line. We first identified candidate motifs by studying 112 pathogenic germ-line GRs in hereditary colorectal cancer patients, and subsequently created an algorithm, termed recombination type ratio, which correctly predicts the propensity of rearrangements with respect to homologous versus nonhomologous recombination events.
Assuntos
Pontos de Quebra do Cromossomo , Recombinação Homóloga , Proteínas Adaptadoras de Transdução de Sinal/genética , Polipose Adenomatosa do Colo/genética , Proteína da Polipose Adenomatosa do Colo/genética , Adenosina Trifosfatases/genética , Antígenos de Neoplasias/genética , Sequência de Bases , Moléculas de Adesão Celular/genética , Mapeamento Cromossômico , Neoplasias Colorretais Hereditárias sem Polipose/genética , Enzimas Reparadoras do DNA/genética , Proteínas de Ligação a DNA/genética , Molécula de Adesão da Célula Epitelial , Humanos , Endonuclease PMS2 de Reparo de Erro de Pareamento , Anotação de Sequência Molecular , Proteína 1 Homóloga a MutL , Proteína 2 Homóloga a MutS/genética , Proteínas Nucleares/genética , Análise de Sequência de DNARESUMO
The genome-wide accumulation of DNA replication errors known as microsatellite instability (MSI) is the hallmark lesion of DNA mismatch repair (MMR)-deficient cancers. Although testing for MSI is widely used to guide clinical management, the contribution of MSI at distinct genic loci to the phenotype remains largely unexplored. Here, we report that a mononucleotide (T/U)16 tract located in the 3' untranslated region (3'-UTR) of the Ewing sarcoma breakpoint region 1 (EWSR1) gene is a novel MSI target locus that shows perfect sensitivity and specificity in detecting mismatch repair-deficient cancers in two independent populations. We further found a striking relocalization of the EWSR1 protein from nucleus to cytoplasm in MMR-deficient cancers and that the nonprotein-coding MSI target locus itself has a modulatory effect on EWSR1 gene expression through alternative 3' end processing of the EWSR1 gene. Our results point to a MSI target gene-specific effect in MMR-deficient cancers.
Assuntos
Regiões 3' não Traduzidas , Proteínas de Ligação a Calmodulina/biossíntese , Neoplasias Colorretais/genética , Reparo de Erro de Pareamento de DNA , Distúrbios no Reparo do DNA , Proteínas de Ligação a RNA/biossíntese , Proteínas de Ligação a Calmodulina/genética , Neoplasias Colorretais Hereditárias sem Polipose/genética , Células HCT116 , Células HT29 , Células HeLa , Humanos , Instabilidade de Microssatélites , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , Proteína EWS de Ligação a RNA , Proteínas de Ligação a RNA/genética , TransfecçãoRESUMO
Many individuals with multiple or large colorectal adenomas or early-onset colorectal cancer (CRC) have no detectable germline mutations in the known cancer predisposition genes. Using whole-genome sequencing, supplemented by linkage and association analysis, we identified specific heterozygous POLE or POLD1 germline variants in several multiple-adenoma and/or CRC cases but in no controls. The variants associated with susceptibility, POLE p.Leu424Val and POLD1 p.Ser478Asn, have high penetrance, and POLD1 mutation was also associated with endometrial cancer predisposition. The mutations map to equivalent sites in the proofreading (exonuclease) domain of DNA polymerases É and δ and are predicted to cause a defect in the correction of mispaired bases inserted during DNA replication. In agreement with this prediction, the tumors from mutation carriers were microsatellite stable but tended to acquire base substitution mutations, as confirmed by yeast functional assays. Further analysis of published data showed that the recently described group of hypermutant, microsatellite-stable CRCs is likely to be caused by somatic POLE mutations affecting the exonuclease domain.
