POLQ Protein, Human (Biotinylated, sf9, His, Avi)

POLQ is a low-fidelity DNA polymerase with helicase activity that promotes microhomology-mediated end-joining (MMEJ), an alternative non-homologous end-joining (NHEJ) machinery required for repairing double-strand breaks during mitosis. MMEJ is an error-prone repair pathway that causes sequence deletions and genomic rearrangements, such as telomere fusions, some of which may lead to cellular transformation. Despite being error-prone, MMEJ protects against chromosomal instability and tumorigenesis (by similar). The polymerase binds directly to resected double-strand break ends, enabling microhomologous sequences in the overhangs to base-pair, then extends each strand using the opposing overhang as a template. It requires partially resected DNA with 2–6 base pairs of microhomology for MMEJ. POLQ lacks proofreading activity and is highly promiscuous, extending ssDNA and partial ssDNA (pssDNA) substrates. It also acts as a DNA helicase, displacing the replication protein A complex (RPA/RP-A) from resected breaks to inhibit homology-directed repair (HR). POLQ may possess lyase activity and is involved in somatic hypermutation of immunoglobulin genes (by similar). Additionally, POLQ-mediated end joining contributes to random integration of exogenous DNA.