Meyahealth
Home
ENES
HomeGeneticsGenePOLH gene
Back to Gene

POLH gene

Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

POLH gene

The POLH gene provides instructions for making DNA polymerase eta, an enzyme essential for replicating damaged DNA and protecting cells from the effects of ultraviolet (UV) radiation.

Normal Function

The POLH gene provides instructions for making a protein called DNA polymerase eta. DNA polymerases are a group of enzymes that "read" sequences of DNA and use them as templates to produce new DNA. These enzymes are important for copying (replicating) cells' genetic material in preparation for cell division. DNA polymerases also play critical roles in DNA repair.

The major function of DNA polymerase eta is to replicate DNA that has been damaged, particularly by ultraviolet (UV) rays from sunlight. Most other DNA polymerases are unable to replicate DNA with this type of damage. 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 activity, which is known as translesion synthesis, allows cells to tolerate some abnormalities created by UV exposure. Without this tolerance, unrepaired DNA damage would block DNA replication and cause the cell to die. 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 variant (also called a mutation) in the replicated DNA.

Health Conditions Related to Genetic Changes

Xeroderma pigmentosum

Several variants in the POLH gene have been found to cause a condition called xeroderma pigmentosum. In particular, POLH gene variants cause the variant type of xeroderma pigmentosum (XP-V). Like the other forms of xeroderma pigmentosum, XP-V is characterized by an increased sensitivity to UV rays from sunlight. However, this form of the disorder is typically not associated with neurological abnormalities, such as delayed development and hearing loss.

Most POLH gene variants prevent the production of any detectable DNA polymerase eta. A loss of this enzyme prevents cells from replicating damaged DNA effectively. Without this mechanism for tolerating DNA damage, errors resulting from exposure to UV rays accumulate in genes that control cell growth and division. These errors cause cells to grow too fast and in an uncontrolled way. As a result, people with XP-V have an increased risk of developing skin cancer in areas where the skin is exposed to sunlight.

Other Names for This Gene

  • FLJ16395
  • FLJ21978
  • POLH_HUMAN
  • polymerase (DNA directed), eta
  • polymerase (DNA) eta
  • RAD30
  • RAD30 homolog A
  • RAD30A
  • xeroderma pigmentosum variant type protein
  • XP-V
  • XPV

Genomic Location

The POLH gene is found on chromosome 6.

Frequently Asked Questions

Children with a POLH mutation often develop freckle‑like dark spots or sunburn‑like lesions on exposed skin within the first year of life. They may also have unusually rapid skin aging, blistering after minimal sun exposure, or a high number of actinic keratoses. If a child shows these signs, especially if they burn easily or develop skin lesions after short sun exposure, a genetic evaluation for POLH should be considered.
Confirmation typically involves a DNA test from a blood or saliva sample. The sample is sent to a specialized laboratory that sequences the POLH gene to look for pathogenic variants. In some cases, functional assays of DNA repair capacity in cultured skin cells may also be performed to support the diagnosis.
Daily protection includes wearing broad‑spectrum SPF 50+ sunscreen on all exposed skin, reapplying every two hours or after swimming or sweating; wearing long‑sleeved clothing, wide‑brimmed hats, and UV‑blocking sunglasses; seeking shade during peak sun hours (10 a.m.–4 p.m.); and avoiding tanning beds or artificial UV sources. Regular skin checks by a dermatologist are also recommended.
While no cure exists, early and aggressive skin surveillance, including annual dermatologic exams and dermoscopy, can catch precancerous lesions early. Some clinicians use topical retinoids or cryotherapy to treat actinic keratoses. In severe cases, prophylactic skin removal or laser therapy may be considered. Gene‑therapy research is ongoing but not yet available for clinical use.===
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.