Related Experiment Video

Updated: Aug 24, 2026

Deficient Pms2, ERCC1, Ku86, CcOI in Field Defects During Progression to Colon Cancer
28:15

Deficient Pms2, ERCC1, Ku86, CcOI in Field Defects During Progression to Colon Cancer

Published on: July 28, 2010

A DNA polymerase beta mutant from colon cancer cells induces mutations

Tieming Lang1, Mausumi Maitra, Daniela Starcevic

  • 1Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06520, USA.

Proceedings of the National Academy of Sciences of the United States of America
|April 13, 2004
PubMed

Insights

Mutations in DNA polymerase beta (pol beta) are linked to cancer. A specific pol beta variant, K289M, increases mutation frequency and may contribute to tumor development.

Area of Science:

  • Molecular Biology
  • Genetics
  • Cancer Research

Background:

  • Approximately 35% of analyzed tumors harbor mutations in the DNA polymerase beta (pol beta) gene.
  • The presence of pol beta mutations in a significant fraction of human tumors suggests a link to cancer development.

Purpose of the Study:

  • To investigate the mutagenic potential of a specific DNA pol beta variant (K289M) identified in colorectal carcinoma.
  • To elucidate the mechanism by which the K289M variant contributes to increased mutation frequency.

Main Methods:

  • Expression of the K289M pol beta variant in mouse L cells with a lambda cII mutational target.
  • Analysis of spontaneous mutation frequency and base substitution patterns.
  • Kinetic analysis of purified K289M protein to assess nucleotide misincorporation efficiency.

Main Results:

  • Expression of K289M resulted in a 2.5-fold increase in overall mutation frequency.
  • A significant 16-fold increase in C to G or G to C base substitutions was observed at a specific site.
  • K289M exhibited significantly higher efficiency in misincorporating dCTP opposite template C and dGTP opposite template G compared to wild-type pol beta.

Conclusions:

  • The K289M pol beta variant demonstrates enhanced nucleotide misincorporation activity.
  • Altered DNA positioning within the enzyme's active site is proposed as the mechanism for misincorporation.
  • These findings suggest that K289M-induced mutations have the potential to drive tumorigenesis or neoplastic progression.

More Related Videos

Quantification of Colonic Stem Cell Mutations07:53

Quantification of Colonic Stem Cell Mutations

Published on: September 25, 2015

Immunofluorescence Imaging of DNA Damage and Repair Foci in Human Colon Cancer Cells05:18

Immunofluorescence Imaging of DNA Damage and Repair Foci in Human Colon Cancer Cells

Published on: June 9, 2020

Related Concept Videos

Spontaneous and Induced Mutations01:30

Spontaneous and Induced Mutations

Spontaneous mutations arise infrequently during DNA replication due to errors in the process. A key factor behind these errors is tautomeric shifts in nitrogenous bases, where bases transition from keto to enol forms or amino to imino forms. This shift can alter base-pairing rules, leading to mutations. Additionally, reactive oxygen species (ROS) arising from aerobic metabolism can damage DNA, resulting in depurination (loss of a purine base) or depyrimidination (loss of a pyrimidine base).
Proofreading01:31

Proofreading

Synthesis of new DNA molecules is carried out by the enzyme DNA polymerase, which adds nucleotides on the daughter strand complementary to the template DNA strand. DNA polymerase has a higher affinity to add the correct base and ensures fidelity during DNA replication. Furthermore,  it exhibits proofreading activity during replication, using an exonuclease domain that cuts off incorrect nucleotides from the nascent DNA strand.
Errors During Replication are Corrected by the DNA Polymerase Enzyme
Proofreading01:43

Proofreading

Synthesis of new DNA molecules starts when DNA polymerase links nucleotides together in a sequence that is complementary to the template DNA strand. DNA polymerase has a higher affinity for the correct base to ensure fidelity in DNA replication. The DNA polymerase furthermore proofreads during replication, using an exonuclease domain that cuts off incorrect nucleotides from the nascent DNA strand.Errors during Replication Are Corrected by the DNA Polymerase EnzymeGenomic DNA is synthesized in...
Cancers Originate from Somatic Mutations in a Single Cell02:21

Cancers Originate from Somatic Mutations in a Single Cell

Cancer arises from mutations in the critical genes that allow healthy cells to escape cell cycle regulation and acquire the ability to proliferate indefinitely. Though originating from a single mutation event in one of the originator cells, cancer progresses when the mutant cell lines continue to gain more and more mutations, and finally, become malignant. For example, chronic myelogenous leukemia (CML) develops initially as a non-lethal increase in white blood cells, which progressively...
Genome Copying Errors02:46

Genome Copying Errors

DNA replication is a well-evolved process that copies millions of base pairs with high fidelity during each cell division. Occasionally a wrong base or a long stretch of wrong bases may get added to the daughter strands. If the errors are left unchecked, cells might accumulate several mutations that might endanger their  survival. Therefore, the copying errors are checked and repaired at three levels.
Mismatch Repair01:20

Mismatch Repair

Organisms are capable of detecting and fixing nucleotide mismatches that occur during DNA replication. This sophisticated process requires identifying the new strand and replacing the erroneous bases with correct nucleotides. Mismatch repair is coordinated by many proteins in both prokaryotes and eukaryotes.
The Mutator Protein Family Plays a Key Role in DNA Mismatch Repair
The human genome has more than 3 billion base pairs of DNA per cell. Prior to cell division, that vast amount of genetic...