Proliferating cell nuclear antigen originally identified as an antigen that is expressed in the nuclei of cells during the DNA synthesis phase of the cell cycle. Part of the protein was sequenced and that sequence was used to allow isolation of a cDNA clone. PCNA helps hold DNA polymerase epsilon (Pol ε) to DNA. PCNA is clamped to DNA through the action of replication factor C (RFC), which is a heteropentameric member of the AAA+ class of ATPases. Expression of PCNA is under the control of E2F transcription factor-containing complexes. Since DNA polymerase epsilon is involved in resynthesis of excised damaged DNA strands during
Pfu DNA polymerase and (1991)Patent 5,545,552 over "Pfu" itself was granted in August 1996. Pfu DNA polymerase "Pfu" DNA polymerase is an enzyme found in the hyperthermophilic archaeon "Pyrococcus furiosus", where it functions to copy the organism's DNA during cell division. In the laboratory setting, "Pfu" is used to amplify DNA in the polymerase chain reaction (PCR), where the enzyme serves the central function of copying a new strand of DNA during each extension step. "Pfu" DNA polymerase has superior thermostability and proofreading properties compared to "Taq" DNA polymerase. Unlike "Taq" DNA polymerase, "Pfu" DNA polymerase possesses 3' to 5' exonuclease proofreading activity,