The POLH gene provides instructions for making DNA polymerase eta. DNA polymerases are a group of enzymes which "read" sequences of DNA and use them as templates to produce new DNA. These enzymes play an important role in replication (copy) for cell division. DNA polymerase also play critical role in DNA repair.
The major function of DNA polymerase eta is to replicate damaged DNA from ultraviolet (UV) rays. Other DNA polymerases are unable to replicate DNA with the damage caused by ultra violet rays. When they reach a segment of damaged DNA, they get stuck and the replication process stalls. However, when DNA polymerase eta encounters damaged DNA, it skips over the abnormal segment and continues copying. This ‘Translesion Synthesis’ activity allows cells to tolerate some abnormalities created by UV exposure. Without this tolerance, unrepaired DNA damage would block DNA replication causing the cell death. Therefore, DNA polymerase eta plays an essential role in protecting cells from some of the effects of DNA damage.
DNA polymerase eta is a relatively "error-prone" polymerase. When it bypasses damaged DNA, it often inserts an incorrect DNA building block (nucleotide). This type of error results in a mutation in the replicated DNA.