Functions of base selection step in human DNA polymerase alpha

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Recent research highlights the role of DNA polymerase (pol) base selection in preventing DNA replication errors.
• The fidelity of DNA replication is essential for maintaining genomic stability.
• DNA polymerase alpha (pol alpha) is a key enzyme in DNA replication.

Purpose of the Study:

• To investigate the role of base selection in human pol alpha fidelity.
• To determine the impact of impaired base selection on genomic stability in human cells.
• To assess the translesion synthesis activity of a mutant pol alpha.

Main Methods:

• Introduced a Leu864 to Phe substitution (L864F) into human pol alpha.
• Performed in vitro LacZ alpha forward mutation assays and steady-state kinetics analyses.
• Established stable HCT116 cell clones expressing L864F pol alpha and conducted mutation assays using the HPRT gene as a reporter.

Main Results:

• The L864F mutation increased the overall mutation rate by 180-fold in vitro.
• L864F pol alpha exhibited reduced discrimination between correct and incorrect nucleotide incorporation and primer termini.
• L864F pol alpha showed increased translesion activity over various DNA damage sites, including O(6)-methyl-G.
• Spontaneous mutation rates were 2.4-fold higher in cells expressing L864F pol alpha.
• Increased mutant frequencies were observed in L864F pol alpha cells under spontaneous and methyl methanesulfonate-induced conditions.

Conclusions:

• The base selection step in human pol alpha is critical for preventing DNA replication errors.
• Impaired base selection in pol alpha leads to decreased genomic integrity.
• These findings underscore the importance of pol alpha's proofreading function in maintaining cellular fidelity.