POLI
Description
The POLI (DNA polymerase iota) is a protein-coding gene located on chromosome 18.
POLI gene encodes DNA polymerase iota, an enzyme found in higher eukaryotes that is believed to have evolved from a gene duplication of Pol η. It is a Y family polymerase involved in translesion synthesis, capable of bypassing 6-4 pyrimidine adducts and abasic sites. Notably, Pol ι has a high frequency of wrong base incorporation. Like many Y family polymerases, Pol ι has low processivity, a large DNA binding pocket, and doesn't undergo conformational changes upon DNA binding. These characteristics enable Pol ι to function as a translesion polymerase. Pol ι exclusively utilizes Hoogsteen base pairing during DNA synthesis, adding adenine opposite thymine in the syn conformation and both cytosine and thymine in the anti conformation across guanine, which it flips to the syn conformation. Xeroderma pigmentosum variant (XPV) cells lack DNA polymerase eta (η), relying on DNA polymerase iota (ι) instead. Exposure of XPV cells to UV light results in a high frequency and unique spectrum of UV-induced mutations, potentially leading to malignant transformation.
POLI is an error-prone DNA polymerase specifically involved in DNA repair. It plays a key role in translesion synthesis, where the regular, high-fidelity DNA polymerases cannot continue and DNA replication stalls. It favors Hoogsteen base pairing in its active site and inserts the correct base with high fidelity opposite an adenosine template. However, it shows low fidelity and efficiency opposite a thymidine template, preferentially inserting guanosine. POLI might contribute to the hypermutation of immunoglobulin genes. It forms a Schiff base with 5'-deoxyribose phosphate at abasic sites but may lack lyase activity.
POLI is also known as RAD30B, RAD3OB, eta2.
