DNA polymerase iota is an

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

that in humans is encoded by the ''POLI''

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

. It is found in higher eukaryotes, and is believed to have arisen from a gene duplication from Pol η. Pol ι, is a Y family polymerase that is involved in translesion synthesis. It can bypass 6-4 pyrimidine adducts and abasic sites and has a high frequency of wrong base incorporation. Like many other Y family polymerases Pol ι, has low processivity, a large DNA binding pocket and doesn't undergo conformational changes when DNA binds. These attributes are what allow Pol ι to carry out its task as a translesion polymerase. Pol ι only uses Hoogsteen base pairing, during DNA synthesis, it will add

adenine Adenine (, ) (nucleoside#List of nucleosides and corresponding nucleobases, symbol A or Ade) is a purine nucleotide base that is found in DNA, RNA, and Adenosine triphosphate, ATP. Usually a white crystalline subtance. The shape of adenine is ...

opposite to

thymine Thymine () (symbol T or Thy) is one of the four nucleotide bases in the nucleic acid of DNA that are represented by the letters G–C–A–T. The others are adenine, guanine, and cytosine. Thymine is also known as 5-methyluracil, a pyrimidine ...

in the syn conformation and can add both

cytosine Cytosine () (symbol C or Cyt) is one of the four nucleotide bases found in DNA and RNA, along with adenine, guanine, and thymine ( uracil in RNA). It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attac ...

and thymine in the anti conformation across

guanine Guanine () (symbol G or Gua) is one of the four main nucleotide bases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine ( uracil in RNA). In DNA, guanine is paired with cytosine. The guanine nucleoside ...

, which it flips to the syn conformation.

Xeroderma pigmentosum variant

Xeroderma pigmentosum variant (XPV) cells lack DNA polymerase eta (η).Wang Y, Woodgate R, McManus TP, Mead S, McCormick JJ, Maher VM. Evidence that in xeroderma pigmentosum variant cells, which lack DNA polymerase eta, DNA polymerase iota causes the very high frequency and unique spectrum of UV-induced mutations. Cancer Res. 2007 Apr 1;67(7):3018-26. doi: 10.1158/0008-5472.CAN-06-3073. PMID: 17409408 Instead these cells use DNA polymerase iota (ι). Exposure of XPV cells to UV light causes a very high frequency and unique spectrum of UV-induced mutations that can ultimately lead to malignant transformation.

Xeroderma pigmentosum variant

References

Further reading