Functional effects of the MLH1-93G>A polymorphism on MLH1/EPM2AIP1 promoter activity

Oncol Rep. 2011 Mar;25(3):809-15. doi: 10.3892/or.2010.1129. Epub 2010 Dec 30.


Defective mismatch repair leads to the microsatellite instability (MSI) phenotype of colorectal cancer (CRC). We previously showed that the MLH1-93G>A promoter polymorphism is strongly associated with MSI tumours, suggesting a modifier role for this polymorphism in CRC. The MLH1 promoter is bi-directional with the EPM2AIP1 gene located on the antisense strand. In order to evaluate the functional effects of this polymorphism, we transfected a panel of CRC, endometrial cancer and non-tumourigenic cell lines with MLH1 luciferase promoter constructs. We used constructs in reverse orientation to assess the effect of this polymorphism on EPM2AIP1. The luciferase activities were compared using a two-sided Student's t-test. Electrophoretic mobility shift assays (EMSAs) were used to evaluate whether differential protein binding was responsible for the differences in promoter activity. We observed a higher level of activity with the -93G allele in all the cell lines observed; including the CRC cell line, HCT116 (P=0.002), the endometrial cancer cell line, HEC-1-A (P<0.001) and the normal colonic cell line, CCD-841-CoTr (P=0.002). This polymorphism also affected EPM2AIP1 transcription with the -93A allele demonstrating higher promoter activity in the HCT116 (P=0.007) and HEC-1-A (P=0.004) cells. The EMSA results suggest that this polymorphism alters the affinity of nuclear factors that bind to this region. Our findings indicate that the -93G>A polymorphism modifies the efficiency of MLH1/EPM2AIP1 transcription.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics*
  • Adaptor Proteins, Signal Transducing / physiology
  • Carcinoma / genetics
  • Carrier Proteins / genetics*
  • Carrier Proteins / physiology
  • Cells, Cultured
  • Colorectal Neoplasms / genetics
  • Gene Expression Regulation, Neoplastic
  • HCT116 Cells
  • HT29 Cells
  • Humans
  • Microsatellite Instability
  • MutL Protein Homolog 1
  • Nuclear Proteins / genetics*
  • Nuclear Proteins / physiology
  • Polymorphism, Single Nucleotide / physiology*
  • Promoter Regions, Genetic / genetics
  • Promoter Regions, Genetic / physiology*
  • Transcription, Genetic
  • Transfection


  • Adaptor Proteins, Signal Transducing
  • Carrier Proteins
  • EPM2AIP1 protein, human
  • MLH1 protein, human
  • Nuclear Proteins
  • MutL Protein Homolog 1