Functional identity of proliferating cell nuclear antigen and a DNA polymerase-δ auxiliary protein

Abstract

The mechanism of replication of the simian virus 40 (SV40) genome closely resembles that of cellular chromosomes, thereby providing an excellent model system for examining the enzymatic requirements for DNA replication. Only one viral gene product, the large tumour antigen (large-T antigen), is required for viral replication, so the majority of replication enzymes must be cellular. Indeed, a number of enzymatic activities associated with replication and the S phase of the cell cycle are induced upon SV40 infection. Cell-free extracts derived from human cells, when supplemented with immunopurified SV40 large-T antigen support efficient replication of plasmids that contain the SV40 origin of DNA replication. Using this system, a cellular protein of relative molecular mass 36,000 (Mr = 36K) that is required for the elongation stage of SV40 DNA replication in vitro has been purified and identified as a known cell-cycle regulated protein, alternatively called the proliferating cell nuclear antigen (PCNA) or cyclin. It was noticed that, in its physical characteristics, PCNA closely resembles a protein that regulates the activity of calf thymus DNA polymerase-delta. Here we show that PCNA and the polymerase-delta auxiliary protein have similar electrophoretic behaviour and are both recognized by anti-PCNA human autoantibodies. More importantly, both proteins are functionally equivalent; they stimulate SV40 DNA replication in vitro and increase the processivity of calf thymus DNA polymerase-delta. These results implicate a novel animal cell DNA polymerase, DNA polymerase-delta, in the elongation stage of replicative DNA synthesis in vitro.

Proliferating activity in differential diagnosis of benign phyllodes tumor and cellular fibroadenomas: Is it helpful?

“…7 On the other hand PCNA is also a non-histone nuclear protein and is present in the late G1 phase, with the peak in G1/S interphase of the cell cycle. 9 As the two markers indicate the different cell cycle phases of proliferating cell, we use both of them. In several studies the determination of proliferating activity and Ki-67 antigen proved to be a useful parameter to distinguish between benign and malignant tumors.…”

Characterization of keratin and cell cycle protein expression in cell lines from squamous intraepithelial lesions progressing towards a malignant phenotype

“…PCNA is normally localized in the nucleus as an essential component of the replication mechanism (Bravo et al, 1987;Prelich et al, 1987). Besides its role in replication, it is directly involved in nucleotide excision repair (Shivji et al, 1992), and elevated expression is detected in response to DNA damage in vivo (Hall et al, 1993).…”

Regulation of human DNA polymerase delta in the cellular responses to DNA damage

“…Molecular cloning of p125 showed that the catalytic core was highly conserved in evolution from T4 bacteriophage to human Hao et al, 1992;Yang et al, 1992], and Pol d is now classified as a member of the B family polymerases. Closely allied with the early history of Pol d are studies of the eukaryotic DNA-sliding clamp, proliferating cell nuclear antigen (PCNA; [Kuriyan and O'Donnell, 1993;Moldovan et al, 2010]), which was discovered as a processivity factor that stimulated Pol d activity [Prelich et al, 1987].…”