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Unique misinsertion specificity of poliota may decrease the mutagenic potential of deaminated cytosines.
1Section on DNA Replication, Repair and Mutagenesis, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-2725, USA.
The EMBO Journal
|November 15, 2001
Summary
DNA polymerase iota (poliota) bypasses DNA lesions, inserting nucleotides opposite uracil and oxidized bases. It preferentially inserts guanine opposite uracil derivatives, potentially reducing mutagenicity.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- DNA polymerase iota (poliota) is a distributive, error-prone enzyme.
- It can incorporate nucleotides opposite various DNA lesions but struggles with further elongation.
Purpose of the Study:
- To investigate poliota's ability to facilitate bypass of uracil and its derivatives, and oxidized cytosine and guanine residues.
- To determine the fidelity of translesion replication by poliota depending on the specific DNA lesion.
Main Methods:
- Assessing nucleotide incorporation opposite DNA lesions by poliota.
- Evaluating primer extension efficiency after misincorporation.
Main Results:
- Polioiota efficiently bypasses uracil, 5-hydroxyuracil, 5,6-dihydrouracil, 8-oxoguanine, and 5-hydroxycytosine.
- It shows a preference for inserting T and G over A opposite uracil and its derivatives.
- G:U, G:5-OHU, and G:5,6-DHU mispairs were extended efficiently, unlike T:U, T:5-OHU, and T:5,6-DHU mispairs.
Conclusions:
- Polioiota facilitates translesion synthesis across uracil and oxidized base lesions.
- The enzyme's preference for inserting guanine opposite uracil derivatives may serve as a cellular mechanism to mitigate the mutagenic effects of cytosine deamination products.