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.
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