Work

Colon Cancer-associated DNA Polymerase β Variant Induces Genomic Instability and Cellular Transformation

Year: 2012

Type: article

Abstract: Rapidly advancing technology has resulted in the generation of the genomic sequences of several human tumors. We have identified several mutations of the DNA polymerase β (pol β) gene in human colorectal cancer. We have demonstrated that the expression of the pol β G231D variant increased chromosomal aberrations and induced cellular transformation. The transformed phenotype persisted in the cells even once the expression of G231D was extinguished, suggesting that it resulted as a consequence of genomic instability. Biochemical analysis revealed that its catalytic rate was 140-fold slower than WT pol β, and this was a result of the decreased binding affinity of nucleotides by G231D. Residue 231 of pol β lies in close proximity to the template strand of the DNA. Molecular modeling demonstrated that the change from a small and nonpolar glycine to a negatively charged aspartate resulted in a repulsion between the template and residue 231 leading to the distortion of the dNTP binding pocket. In addition, expression of G231D was insufficient to rescue pol β-deficient cells treated with chemotherapeutic agents suggesting that these agents may be effectively used to treat tumors harboring this mutation. More importantly, this suggests that the G231D variant has impaired base excision repair. Together, these data indicate that the G231D variant plays a role in driving cancer. Background: Mutations in the POLB gene are present in 40% of human colorectal tumors. Results: The G231D variant is a slow polymerase that induces genomic instability and cellular transformation. Conclusion: The slow G231D variant induces cellular transformation due to its inability to fill in single nucleotide gaps. Significance: Slow pol β variants may drive tumorigenesis.

Source: Journal of Biological Chemistry

DOI: 10.1074/jbc.m112.362111

Authors: Antonia A. Nemec, Katherine A. Donigan, Drew L. Murphy, Joachim Jaeger, Joann B. Sweasy

Institutions: Yale University, New York State Department of Health, Wadsworth Center

Language: English

Topic: DNA Repair Mechanisms

Subfield: Molecular Biology

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

SDG: Good health and well-being

Open Access status: hybrid

Estimated APC paid: $3,430