POLR3H, also as known as A1665 and RPC8, belongs to the eukaryotic RPB7/RPC8 RNA polymerase subunit family. POLR3H is DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates. It plays a key role in sensing and limiting infection by intracellular bacteria and DNA viruses. POLR3H acts as nuclear and cytosolic DNA sensor involved in innate immune response. Recombinant human POLR3H protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.