Error-prone lesion bypass by human DNA polymerase eta.

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• DNA lesion bypass is crucial for maintaining genomic integrity during replication.
• Human DNA polymerase eta (Pol(eta)), encoded by the Xeroderma pigmentosum variant (XPV) gene, is primarily known for error-free translesion synthesis opposite TT dimers.

Purpose of the Study:

• To investigate the in vitro DNA lesion bypass capabilities of human Pol(eta) opposite various DNA lesions beyond TT dimers.
• To determine the fidelity and nucleotide incorporation patterns of Pol(eta) when encountering different types of DNA damage.

Main Methods:

• Purified human Pol(eta) was used to assess its bypass activity against template DNA lesions including 8-oxoguanine, abasic sites, and benzo[a]pyrene-N2-dG adducts.
• Nucleotide incorporation opposite these lesions was analyzed to determine bypass efficiency and fidelity.

Main Results:

• Human Pol(eta) efficiently bypassed 8-oxoguanine, incorporating A or C with similar frequencies.
• Pol(eta) effectively bypassed abasic sites, incorporating A more frequently than G, and caused -1 deletions when a T preceded the abasic site.
• Bypass of (+)-trans-anti-benzo[a]pyrene-N2-dG was partial, with a preference for incorporating A, correlating with known mutation spectra in mammalian cells.

Conclusions:

• Human Pol(eta) exhibits error-prone translesion DNA synthesis capabilities in vitro.
• Pol(eta) may contribute to mutagenesis by bypassing certain DNA lesions in a manner that leads to genetic alterations in humans.