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
Cell-free fetal DNA of laboratory methods have been developed for cell-free fetal DNA screening for genetic defects have been developed. The main ones are (1) massively parallel shotgun sequencing (MPSS), (2) targeted massive parallel sequencing (t-MPS) and (3) single nucleotide polymorphism (SNP) based approach. A maternal peripheral blood sample is taken by venesection at about ten weeks gestation. Blood plasma is separated from the maternal blood sample using a laboratory centrifuge. The cffDNA is then isolated and purified. A standardized protocol for doing this was written through an evaluation of the scientific literature. The highest yield in cffDNA extraction was obtained with the