Polk mutant mice have a spontaneous mutator phenotype

Area of Science:

• Genetics and Molecular Biology
• DNA Repair Mechanisms
• Mammalian Genetics

Background:

• The Polk gene encodes DNA polymerase kappa (Pol kappa), a key enzyme in DNA repair.
• Mice lacking functional Polk display no obvious outward health issues.
• Previous research has not fully elucidated the in vivo role of Pol kappa in spontaneous mutagenesis.

Purpose of the Study:

• To investigate the potential for a spontaneous mutator phenotype in mice deficient for DNA polymerase kappa (Polk).
• To quantitatively and qualitatively assess mutagenesis in various tissues of Polk(-/-) mice.
• To determine the specific types of DNA mutations occurring in the absence of Pol kappa.

Main Methods:

• Utilized Polk(-/-) mice and isogenic wild-type controls.
• Employed a reporter transgene (lambda-phage cII gene) for mutation detection.
• Conducted quantitative and qualitative mutagenesis studies across multiple tissues, including kidney, liver, lung, spleen, and testis.

Main Results:

• Polk(-/-) mice exhibited significantly increased spontaneous mutation frequencies in the kidney, liver, and lung.
• No significant increase in mutation frequency was observed in the spleen or testis of Polk(-/-) mice.
• The mutation spectra in affected tissues were dominated by G:C base pair alterations.

Conclusions:

• DNA polymerase kappa (Polk) is essential for accurate translesion DNA synthesis, particularly past DNA adducts.
• Pol kappa likely plays a critical role in repairing naturally occurring polycyclic guanine adducts, potentially derived from cholesterol metabolites.
• The absence of Pol kappa leads to increased spontaneous mutations in specific organs, highlighting its importance in maintaining genomic stability.