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Lesion bypass activities of human DNA polymerase mu
Yanbin Zhang1, Xiaohua Wu, Dongyu Guo
1Graduate Center for Toxicology, University of Kentucky, Lexington 40536, USA.
Abstract:
DNA polymerase mu (Polmu) is a newly discovered member of the polymerase X family with unknown cellular function. The understanding of Polmu function should be facilitated by an understanding of its biochemical activities. By using purified human Polmu for biochemical analyses, we discovered the lesion bypass activities of this polymerase in response to several types of DNA damage. When it encountered a template 8-oxoguanine, abasic site, or 1,N(6)-ethenoadenine, purified human Polmu efficiently bypassed the lesion. Even bulky DNA adducts such as N-2-acetylaminofluorene-adducted guanine, (+)- and (-)-trans-anti-benzo[a]pyrene-N(2)-dG were unable to block the polymerase activity of human Polmu. Bypass of these simple base damage and bulky adducts was predominantly achieved by human Polmu through a deletion mechanism. The Polmu specificity of nucleotide incorporation indicates that the deletion resulted from primer realignment before translesion synthesis. Purified human Polmu also effectively bypassed a template cis-syn TT dimer. However, this bypass was achieved in a mainly error-free manner with AA incorporation opposite the TT dimer. These results provide new insights into the biochemistry of human Polmu and show that efficient translesion synthesis activity is not strictly confined to the Y family polymerases.
Insights
DNA polymerase mu (Polmu) efficiently bypasses various DNA lesions, including bulky adducts and UV damage. This polymerase exhibits translesion synthesis, primarily through a deletion mechanism, challenging existing polymerase family classifications.
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- DNA polymerase mu (Polmu) is a recently identified member of the polymerase X family.
- Its specific cellular functions and biochemical activities remain largely uncharacterized.
Purpose of the Study:
- To elucidate the biochemical activities and DNA damage bypass capabilities of human Polmu.
- To understand the mechanism by which Polmu handles various DNA lesions.
Main Methods:
- Purified human Polmu was used for in vitro biochemical analyses.
- Lesion bypass assays were performed using templates containing various DNA damages, including oxidative damage, abasic sites, bulky adducts, and UV-induced dimers.
Main Results:
- Human Polmu efficiently bypassed 8-oxoguanine, abasic sites, and 1,N(6)-ethenoadenine.
- The polymerase also bypassed bulky DNA adducts like N-2-acetylaminofluorene and benzo[a]pyrene adducts, predominantly via a deletion mechanism.
- Polmu effectively bypassed cis-syn TT dimers in an error-free manner, incorporating AA opposite the lesion.
- These bypass mechanisms involved primer realignment before translesion synthesis.
Conclusions:
- Human Polmu possesses significant translesion synthesis capabilities, including bypass of diverse DNA lesions.
- The polymerase utilizes a deletion mechanism for bypassing many base damages and bulky adducts.
- Polmu's error-free bypass of UV dimers highlights its versatility.
- These findings suggest that efficient translesion synthesis is not exclusive to Y-family polymerases.